Implement browsing context discarding.

components/constellation/constellation.rs

@@ -95,7 +95,7 @@ use profile_traits::mem;
 use profile_traits::time;
 use rand::{Rng, SeedableRng, StdRng, random};
 use script_traits::{AnimationState, AnimationTickType, CompositorEvent};
-use script_traits::{ConstellationControlMsg, ConstellationMsg as FromCompositorMsg};
+use script_traits::{ConstellationControlMsg, ConstellationMsg as FromCompositorMsg, DiscardBrowsingContext};
 use script_traits::{DocumentState, LayoutControlMsg, LoadData};
 use script_traits::{IFrameLoadInfo, IFrameLoadInfoWithData, IFrameSandboxState, TimerEventRequest};
 use script_traits::{LayoutMsg as FromLayoutMsg, ScriptMsg as FromScriptMsg, ScriptThreadFactory};
@@ -975,13 +975,11 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
                 debug!("constellation got set visibility change complete message");
                 self.handle_visibility_change_complete(pipeline_id, visible);
             }
-            FromScriptMsg::RemoveIFrame(pipeline_id, sender) => {
+            FromScriptMsg::RemoveIFrame(frame_id, sender) => {
                 debug!("constellation got remove iframe message");
-                self.handle_remove_iframe_msg(pipeline_id);
+                let removed_pipeline_ids = self.handle_remove_iframe_msg(frame_id);
-                if let Some(sender) = sender {
+                if let Err(e) = sender.send(removed_pipeline_ids) {
-                    if let Err(e) = sender.send(()) {
+                    warn!("Error replying to remove iframe ({})", e);
-                        warn!("Error replying to remove iframe ({})", e);
-                    }
                 }
             }
             FromScriptMsg::NewFavicon(url) => {
@@ -1126,7 +1124,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
             debug!("Removing pending frame {}.", pending.frame_id);
             self.close_frame(pending.frame_id, ExitPipelineMode::Normal);
             debug!("Removing pending pipeline {}.", pending.new_pipeline_id);
-            self.close_pipeline(pending.new_pipeline_id, ExitPipelineMode::Normal);
+            self.close_pipeline(pending.new_pipeline_id, DiscardBrowsingContext::Yes, ExitPipelineMode::Normal);
         }
 
         // In case there are frames which weren't attached to the frame tree, we close them.
@@ -1140,7 +1138,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         let pipeline_ids: Vec<PipelineId> = self.pipelines.keys().cloned().collect();
         for pipeline_id in pipeline_ids {
             debug!("Removing detached pipeline {}.", pipeline_id);
-            self.close_pipeline(pipeline_id, ExitPipelineMode::Normal);
+            self.close_pipeline(pipeline_id, DiscardBrowsingContext::Yes, ExitPipelineMode::Normal);
         }
     }
 
@@ -1234,7 +1232,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         let parent_info = pipeline_id.and_then(|id| self.pipelines.get(&id).and_then(|pipeline| pipeline.parent_info));
         let window_size = pipeline_id.and_then(|id| self.pipelines.get(&id).and_then(|pipeline| pipeline.size));
 
-        self.close_frame_children(top_level_frame_id, ExitPipelineMode::Force);
+        self.close_frame_children(top_level_frame_id, DiscardBrowsingContext::No, ExitPipelineMode::Force);
 
         let failure_url = ServoUrl::parse("about:failure").expect("infallible");
 
@@ -1805,20 +1803,14 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         self.focus_parent_pipeline(pipeline_id);
     }
 
-    fn handle_remove_iframe_msg(&mut self, pipeline_id: PipelineId) {
+    fn handle_remove_iframe_msg(&mut self, frame_id: FrameId) -> Vec<PipelineId> {
-        let frame_id = self.pipelines.get(&pipeline_id).map(|pipeline| pipeline.frame_id);
+        let result = self.full_frame_tree_iter(frame_id)
-        match frame_id {
+            .flat_map(|frame| frame.next.iter().chain(frame.prev.iter())
-            Some(frame_id) => {
+                      .filter_map(|entry| entry.pipeline_id)
-                // This iframe has already loaded and been added to the frame tree.
+                      .chain(once(frame.pipeline_id)))
-                self.close_frame(frame_id, ExitPipelineMode::Normal);
+            .collect();
-            }
+        self.close_frame(frame_id, ExitPipelineMode::Normal);
-            None => {
+        result
-                // This iframe is currently loading / painting for the first time.
-                // In this case, it doesn't exist in the frame tree, but the pipeline
-                // still needs to be shut down.
-                self.close_pipeline(pipeline_id, ExitPipelineMode::Normal);
-            }
-        }
     }
 
     fn handle_set_visible_msg(&mut self, pipeline_id: PipelineId, visible: bool) {
@@ -2118,7 +2110,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         };
 
         if let Some(evicted_id) = evicted_id {
-            self.close_pipeline(evicted_id, ExitPipelineMode::Normal);
+            self.close_pipeline(evicted_id, DiscardBrowsingContext::No, ExitPipelineMode::Normal);
         }
 
         if new_frame {
@@ -2344,7 +2336,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
             };
             for entry in evicted {
                 if let Some(pipeline_id) = entry.pipeline_id {
-                    self.close_pipeline(pipeline_id, ExitPipelineMode::Normal);
+                    self.close_pipeline(pipeline_id, DiscardBrowsingContext::No, ExitPipelineMode::Normal);
                 }
             }
         }
@@ -2357,7 +2349,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
             .and_then(|frame| self.pipelines.get(&frame.pipeline_id))
             .and_then(|pipeline| pipeline.parent_info);
 
-        self.close_frame_children(frame_id, exit_mode);
+        self.close_frame_children(frame_id, DiscardBrowsingContext::Yes, exit_mode);
 
         self.event_loops.remove(&frame_id);
         if self.frames.remove(&frame_id).is_none() {
@@ -2375,7 +2367,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
     }
 
     // Close the children of a frame
-    fn close_frame_children(&mut self, frame_id: FrameId, exit_mode: ExitPipelineMode) {
+    fn close_frame_children(&mut self, frame_id: FrameId, dbc: DiscardBrowsingContext, exit_mode: ExitPipelineMode) {
         debug!("Closing frame children {}.", frame_id);
         // Store information about the pipelines to be closed. Then close the
         // pipelines, before removing ourself from the frames hash map. This
@@ -2393,18 +2385,18 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
         }
 
         for pipeline_id in pipelines_to_close {
-            self.close_pipeline(pipeline_id, exit_mode);
+            self.close_pipeline(pipeline_id, dbc, exit_mode);
         }
 
         debug!("Closed frame children {}.", frame_id);
     }
 
     // Close all pipelines at and beneath a given frame
-    fn close_pipeline(&mut self, pipeline_id: PipelineId, exit_mode: ExitPipelineMode) {
+    fn close_pipeline(&mut self, pipeline_id: PipelineId, dbc: DiscardBrowsingContext, exit_mode: ExitPipelineMode) {
         debug!("Closing pipeline {:?}.", pipeline_id);
         // Store information about the frames to be closed. Then close the
         // frames, before removing ourself from the pipelines hash map. This
-        // ordering is vital - so that if close_frames() ends up closing
+        // ordering is vital - so that if close_frame() ends up closing
         // any child pipelines, they can be removed from the parent pipeline correctly.
         let frames_to_close = {
             let mut frames_to_close = vec!();
@@ -2438,8 +2430,8 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
 
         // Inform script, compositor that this pipeline has exited.
         match exit_mode {
-            ExitPipelineMode::Normal => pipeline.exit(),
+            ExitPipelineMode::Normal => pipeline.exit(dbc),
-            ExitPipelineMode::Force => pipeline.force_exit(),
+            ExitPipelineMode::Force => pipeline.force_exit(dbc),
         }
         debug!("Closed pipeline {:?}.", pipeline_id);
     }
@@ -2463,7 +2455,7 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
                         // Note that we deliberately do not do any of the tidying up
                         // associated with closing a pipeline. The constellation should cope!
                         warn!("Randomly closing pipeline {}.", pipeline_id);
-                        pipeline.force_exit();
+                        pipeline.force_exit(DiscardBrowsingContext::No);
                     }
                 }
             }

components/constellation/pipeline.rs

@@ -20,7 +20,7 @@ use net_traits::{IpcSend, ResourceThreads};
 use net_traits::image_cache_thread::ImageCacheThread;
 use profile_traits::mem as profile_mem;
 use profile_traits::time;
-use script_traits::{ConstellationControlMsg, InitialScriptState};
+use script_traits::{ConstellationControlMsg, DiscardBrowsingContext, InitialScriptState};
 use script_traits::{LayoutControlMsg, LayoutMsg, LoadData, MozBrowserEvent};
 use script_traits::{NewLayoutInfo, SWManagerMsg, SWManagerSenders, ScriptMsg};
 use script_traits::{ScriptThreadFactory, TimerEventRequest, WindowSizeData};
@@ -328,7 +328,7 @@ impl Pipeline {
 
     /// A normal exit of the pipeline, which waits for the compositor,
     /// and delegates layout shutdown to the script thread.
-    pub fn exit(&self) {
+    pub fn exit(&self, discard_bc: DiscardBrowsingContext) {
         debug!("pipeline {:?} exiting", self.id);
 
         // The compositor wants to know when pipelines shut down too.
@@ -345,15 +345,17 @@ impl Pipeline {
 
         // Script thread handles shutting down layout, and layout handles shutting down the painter.
         // For now, if the script thread has failed, we give up on clean shutdown.
-        if let Err(e) = self.event_loop.send(ConstellationControlMsg::ExitPipeline(self.id)) {
+        let msg = ConstellationControlMsg::ExitPipeline(self.id, discard_bc);
+        if let Err(e) = self.event_loop.send(msg) {
             warn!("Sending script exit message failed ({}).", e);
         }
     }
 
     /// A forced exit of the shutdown, which does not wait for the compositor,
     /// or for the script thread to shut down layout.
-    pub fn force_exit(&self) {
+    pub fn force_exit(&self, discard_bc: DiscardBrowsingContext) {
-        if let Err(e) = self.event_loop.send(ConstellationControlMsg::ExitPipeline(self.id)) {
+        let msg = ConstellationControlMsg::ExitPipeline(self.id, discard_bc);
+        if let Err(e) = self.event_loop.send(msg) {
             warn!("Sending script exit message failed ({}).", e);
         }
         if let Err(e) = self.layout_chan.send(LayoutControlMsg::ExitNow) {

components/script/dom/browsingcontext.rs

@@ -3,16 +3,13 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::bindings::conversions::{ToJSValConvertible, root_from_handleobject};
-use dom::bindings::inheritance::Castable;
+use dom::bindings::js::{JS, Root, RootedReference};
-use dom::bindings::js::{JS, MutNullableJS, Root, RootedReference};
 use dom::bindings::proxyhandler::{fill_property_descriptor, get_property_descriptor};
 use dom::bindings::reflector::{DomObject, MutDomObject, Reflector};
 use dom::bindings::trace::JSTraceable;
 use dom::bindings::utils::WindowProxyHandler;
 use dom::bindings::utils::get_array_index_from_id;
-use dom::document::Document;
 use dom::element::Element;
-use dom::globalscope::GlobalScope;
 use dom::window::Window;
 use js::JSCLASS_IS_GLOBAL;
 use js::glue::{CreateWrapperProxyHandler, ProxyTraps, NewWindowProxy};
@@ -26,7 +23,6 @@ use js::jsapi::{MutableHandle, MutableHandleObject, MutableHandleValue};
 use js::jsapi::{ObjectOpResult, PropertyDescriptor};
 use js::jsval::{UndefinedValue, PrivateValue};
 use js::rust::get_object_class;
-use msg::constellation_msg::PipelineId;
 use std::cell::Cell;
 
 #[dom_struct]
@@ -40,10 +36,8 @@ pub struct BrowsingContext {
     /// Indicates if reflow is required when reloading.
     needs_reflow: Cell<bool>,
 
-    /// The current active document.
+    /// Has this browsing context been discarded?
-    /// Note that the session history is stored in the constellation,
+    discarded: Cell<bool>,
-    /// in the script thread we just track the current active document.
-    active_document: MutNullableJS<Document>,
 
     /// The containing iframe element, if this is a same-origin iframe
     frame_element: Option<JS<Element>>,
@@ -54,7 +48,7 @@ impl BrowsingContext {
         BrowsingContext {
             reflector: Reflector::new(),
             needs_reflow: Cell::new(true),
-            active_document: Default::default(),
+            discarded:  Cell::new(false),
             frame_element: frame_element.map(JS::from_ref),
         }
     }
@@ -84,20 +78,12 @@ impl BrowsingContext {
         }
     }
 
-    pub fn set_active_document(&self, document: &Document) {
+    pub fn discard(&self) {
-        self.active_document.set(Some(document))
+        self.discarded.set(true);
     }
 
-    pub fn active_document(&self) -> Root<Document> {
+    pub fn is_discarded(&self) -> bool {
-        self.active_document.get().expect("No active document.")
+        self.discarded.get()
-    }
-
-    pub fn maybe_active_document(&self) -> Option<Root<Document>> {
-        self.active_document.get()
-    }
-
-    pub fn active_window(&self) -> Root<Window> {
-        Root::from_ref(self.active_document().window())
     }
 
     pub fn frame_element(&self) -> Option<&Element> {
@@ -115,15 +101,6 @@ impl BrowsingContext {
         self.needs_reflow.set(status);
         old
     }
-
-    pub fn active_pipeline_id(&self) -> Option<PipelineId> {
-        self.active_document.get()
-            .map(|doc| doc.window().upcast::<GlobalScope>().pipeline_id())
-    }
-
-    pub fn unset_active_document(&self) {
-        self.active_document.set(None)
-    }
 }
 
 #[allow(unsafe_code)]

components/script/dom/document.rs

@@ -190,6 +190,7 @@ pub struct Document {
     last_modified: Option<String>,
     encoding: Cell<EncodingRef>,
     is_html_document: bool,
+    is_fully_active: Cell<bool>,
     url: DOMRefCell<ServoUrl>,
     quirks_mode: Cell<QuirksMode>,
     /// Caches for the getElement methods
@@ -385,20 +386,17 @@ impl Document {
         self.trigger_mozbrowser_event(MozBrowserEvent::SecurityChange(https_state));
     }
 
-    // https://html.spec.whatwg.org/multipage/#active-document
-    pub fn is_active(&self) -> bool {
-        self.browsing_context().map_or(false, |context| {
-            self == &*context.active_document()
-        })
-    }
-
     // https://html.spec.whatwg.org/multipage/#fully-active
     pub fn is_fully_active(&self) -> bool {
-        if !self.is_active() {
+        self.is_fully_active.get()
-            return false;
+    }
-        }
+
-        // FIXME: It should also check whether the browser context is top-level or not
+    pub fn fully_activate(&self) {
-        true
+        self.is_fully_active.set(true)
+    }
+
+    pub fn fully_deactivate(&self) {
+        self.is_fully_active.set(false)
     }
 
     pub fn origin(&self) -> &Origin {
@@ -1693,11 +1691,16 @@ impl Document {
         self.current_parser.get()
     }
 
-    /// Find an iframe element in the document.
+    /// Iterate over all iframes in the document.
-    pub fn find_iframe(&self, frame_id: FrameId) -> Option<Root<HTMLIFrameElement>> {
+    pub fn iter_iframes(&self) -> impl Iterator<Item=Root<HTMLIFrameElement>> {
         self.upcast::<Node>()
             .traverse_preorder()
             .filter_map(Root::downcast::<HTMLIFrameElement>)
+    }
+
+    /// Find an iframe element in the document.
+    pub fn find_iframe(&self, frame_id: FrameId) -> Option<Root<HTMLIFrameElement>> {
+        self.iter_iframes()
             .find(|node| node.frame_id() == frame_id)
     }
 
@@ -1864,6 +1867,7 @@ impl Document {
             // https://dom.spec.whatwg.org/#concept-document-encoding
             encoding: Cell::new(UTF_8),
             is_html_document: is_html_document == IsHTMLDocument::HTMLDocument,
+            is_fully_active: Cell::new(false),
             id_map: DOMRefCell::new(HashMap::new()),
             tag_map: DOMRefCell::new(HashMap::new()),
             tagns_map: DOMRefCell::new(HashMap::new()),
@@ -2261,19 +2265,12 @@ impl DocumentMethods for Document {
 
     // https://html.spec.whatwg.org/multipage/#dom-document-hasfocus
     fn HasFocus(&self) -> bool {
-        match self.browsing_context() {
+        // Step 1-2.
-            Some(browsing_context) => {
+        if self.window().parent_info().is_none() && self.is_fully_active() {
-                // Step 2.
+            return true;
-                let candidate = browsing_context.active_document();
-                // Step 3.
-                if &*candidate == self {
-                    true
-                } else {
-                    false //TODO  Step 4.
-                }
-            }
-            None => false,
         }
+        // TODO Step 3.
+        false
     }
 
     // https://html.spec.whatwg.org/multipage/#relaxing-the-same-origin-restriction
@@ -3190,8 +3187,8 @@ impl DocumentMethods for Document {
 
         // Step 2.
         // TODO: handle throw-on-dynamic-markup-insertion counter.
-
+        // FIXME: this should check for being active rather than fully active
-        if !self.is_active() {
+        if !self.is_fully_active() {
             // Step 3.
             return Ok(());
         }

components/script/dom/htmliframeelement.rs

@@ -33,7 +33,6 @@ use dom::eventtarget::EventTarget;
 use dom::globalscope::GlobalScope;
 use dom::htmlelement::HTMLElement;
 use dom::node::{Node, NodeDamage, UnbindContext, document_from_node, window_from_node};
-use dom::urlhelper::UrlHelper;
 use dom::virtualmethods::VirtualMethods;
 use dom::window::{ReflowReason, Window};
 use html5ever_atoms::LocalName;
@@ -709,42 +708,34 @@ impl VirtualMethods for HTMLIFrameElement {
         LoadBlocker::terminate(&mut blocker);
 
         // https://html.spec.whatwg.org/multipage/#a-browsing-context-is-discarded
-        if let Some(pipeline_id) = self.pipeline_id.get() {
+        debug!("Unbinding frame {}.", self.frame_id);
-            debug!("Unbinding pipeline {} from frame {}.", pipeline_id, self.frame_id);
+        let window = window_from_node(self);
-            let window = window_from_node(self);
+        let (sender, receiver) = ipc::channel().unwrap();
 
-            // The only reason we're waiting for the iframe to be totally
+        // Ask the constellation to remove the iframe, and tell us the
-            // removed is to ensure the script thread can't add iframes faster
+        // pipeline ids of the closed pipelines.
-            // than the compositor can remove them.
+        let msg = ConstellationMsg::RemoveIFrame(self.frame_id, sender);
-            //
+        window.upcast::<GlobalScope>().constellation_chan().send(msg).unwrap();
-            // Since most of this cleanup doesn't happen on same-origin
+        let exited_pipeline_ids = receiver.recv().unwrap();
-            // iframes, and since that would cause a deadlock, don't do it.
+
-            let same_origin = {
+        // The spec for discarding is synchronous,
-                // FIXME(#10968): this should probably match the origin check in
+        // so we need to discard the browsing contexts now, rather than
-                //                HTMLIFrameElement::contentDocument.
+        // when the `PipelineExit` message arrives.
-                let self_url = self.get_url();
+        for exited_pipeline_id in exited_pipeline_ids {
-                let win_url = window_from_node(self).get_url();
+            if let Some(exited_document) = ScriptThread::find_document(exited_pipeline_id) {
-                UrlHelper::SameOrigin(&self_url, &win_url) || self_url.as_str() == "about:blank"
+                exited_document.window().browsing_context().discard();
-            };
+                for exited_iframe in exited_document.iter_iframes() {
-            let (sender, receiver) = if same_origin {
+                    exited_iframe.pipeline_id.set(None);
-                (None, None)
+                }
-            } else {
-                let (sender, receiver) = ipc::channel().unwrap();
-                (Some(sender), Some(receiver))
-            };
-            let msg = ConstellationMsg::RemoveIFrame(pipeline_id, sender);
-            window.upcast::<GlobalScope>().constellation_chan().send(msg).unwrap();
-            if let Some(receiver) = receiver {
-                receiver.recv().unwrap()
             }
-
-            // Resetting the pipeline_id to None is required here so that
-            // if this iframe is subsequently re-added to the document
-            // the load doesn't think that it's a navigation, but instead
-            // a new iframe. Without this, the constellation gets very
-            // confused.
-            self.pipeline_id.set(None);
         }
+
+        // Resetting the pipeline_id to None is required here so that
+        // if this iframe is subsequently re-added to the document
+        // the load doesn't think that it's a navigation, but instead
+        // a new iframe. Without this, the constellation gets very
+        // confused.
+        self.pipeline_id.set(None);
     }
 }
 

components/script/dom/webidls/Window.webidl

@@ -31,9 +31,13 @@
   // other browsing contexts
   [Replaceable] readonly attribute WindowProxy frames;
   //[Replaceable] readonly attribute unsigned long length;
-  [Unforgeable] readonly attribute WindowProxy top;
+  // Note that this can return null in the case that the browsing context has been discarded.
+  // https://github.com/whatwg/html/issues/2115
+  [Unforgeable] readonly attribute WindowProxy? top;
   //         attribute any opener;
-  readonly attribute WindowProxy parent;
+  // Note that this can return null in the case that the browsing context has been discarded.
+  // https://github.com/whatwg/html/issues/2115
+  readonly attribute WindowProxy? parent;
   readonly attribute Element? frameElement;
   //WindowProxy open(optional DOMString url = "about:blank", optional DOMString target = "_blank",
   //                 optional DOMString features = "", optional boolean replace = false);

components/script/dom/window.rs

@@ -163,6 +163,7 @@ pub struct Window {
     #[ignore_heap_size_of = "channels are hard"]
     image_cache_chan: ImageCacheChan,
     browsing_context: MutNullableJS<BrowsingContext>,
+    document: MutNullableJS<Document>,
     history: MutNullableJS<History>,
     performance: MutNullableJS<Performance>,
     navigation_start: u64,
@@ -443,7 +444,7 @@ impl WindowMethods for Window {
 
     // https://html.spec.whatwg.org/multipage/#dom-document-2
     fn Document(&self) -> Root<Document> {
-        self.browsing_context().active_document()
+        self.document.get().expect("Document accessed before initialization.")
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-history
@@ -551,21 +552,32 @@ impl WindowMethods for Window {
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-parent
-    fn Parent(&self) -> Root<BrowsingContext> {
+    fn GetParent(&self) -> Option<Root<BrowsingContext>> {
-        match  self.parent() {
+        // Steps 1. and 2.
-            Some(window) => window.browsing_context(),
+        if self.browsing_context().is_discarded() {
-            None => self.Window()
+            return None;
         }
-    }
+        match self.parent() {
+            // Step 4.
+            Some(parent) => Some(parent.Window()),
+            // Step 5.
+            None => Some(self.Window())
+        }
+     }
 
     // https://html.spec.whatwg.org/multipage/#dom-top
-    fn Top(&self) -> Root<BrowsingContext> {
+    fn GetTop(&self) -> Option<Root<BrowsingContext>> {
+        // Steps 1. and 2.
+        if self.browsing_context().is_discarded() {
+            return None;
+        }
+        // Step 5.
         let mut window = Root::from_ref(self);
         while let Some(parent) = window.parent() {
             window = parent;
         }
-        window.browsing_context()
+        Some(window.Window())
-    }
+     }
 
     // https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/
     // NavigationTiming/Overview.html#sec-window.performance-attribute
@@ -1351,6 +1363,13 @@ impl Window {
         unsafe { SetWindowProxy(cx, window, browsing_context.reflector().get_jsobject()); }
     }
 
+    #[allow(unsafe_code)]
+    pub fn init_document(&self, document: &Document) {
+        assert!(self.document.get().is_none());
+        assert!(document.window() == self);
+        self.document.set(Some(&document));
+    }
+
     /// Commence a new URL load which will either replace this window or scroll to a fragment.
     pub fn load_url(&self, url: ServoUrl, replace: bool, force_reload: bool,
                     referrer_policy: Option<ReferrerPolicy>) {
@@ -1518,13 +1537,8 @@ impl Window {
             return None;
         }
 
-        let browsing_context = self.browsing_context();
+        self.browsing_context().frame_element()
-
+            .map(|frame_element| window_from_node(frame_element))
-        browsing_context.frame_element().map(|frame_element| {
-            let window = window_from_node(frame_element);
-            let context = window.browsing_context();
-            context.active_window()
-        })
     }
 
     /// Returns whether this window is mozbrowser.
@@ -1610,6 +1624,7 @@ impl Window {
             image_cache_thread: image_cache_thread,
             history: Default::default(),
             browsing_context: Default::default(),
+            document: Default::default(),
             performance: Default::default(),
             navigation_start: (current_time.sec * 1000 + current_time.nsec as i64 / 1000000) as u64,
             navigation_start_precise: time::precise_time_ns() as f64,

components/script/script_thread.rs

@@ -83,7 +83,7 @@ use profile_traits::time::{self, ProfilerCategory, profile};
 use script_layout_interface::message::{self, NewLayoutThreadInfo, ReflowQueryType};
 use script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory, EnqueuedPromiseCallback};
 use script_runtime::{ScriptPort, StackRootTLS, get_reports, new_rt_and_cx, PromiseJobQueue};
-use script_traits::{CompositorEvent, ConstellationControlMsg, EventResult};
+use script_traits::{CompositorEvent, ConstellationControlMsg, DiscardBrowsingContext, EventResult};
 use script_traits::{InitialScriptState, LayoutMsg, LoadData, MouseButton, MouseEventType, MozBrowserEvent};
 use script_traits::{NewLayoutInfo, ScriptMsg as ConstellationMsg};
 use script_traits::{ScriptThreadFactory, TimerEvent, TimerEventRequest, TimerSource};
@@ -1007,8 +1007,8 @@ impl ScriptThread {
                 self.handle_css_error_reporting(pipeline_id, filename, line, column, msg),
             ConstellationControlMsg::Reload(pipeline_id) =>
                 self.handle_reload(pipeline_id),
-            ConstellationControlMsg::ExitPipeline(pipeline_id) =>
+            ConstellationControlMsg::ExitPipeline(pipeline_id, discard_browsing_context) =>
-                self.handle_exit_pipeline_msg(pipeline_id),
+                self.handle_exit_pipeline_msg(pipeline_id, discard_browsing_context),
             msg @ ConstellationControlMsg::AttachLayout(..) |
             msg @ ConstellationControlMsg::Viewport(..) |
             msg @ ConstellationControlMsg::SetScrollState(..) |
@@ -1368,6 +1368,7 @@ impl ScriptThread {
                 }
             }
             document.window().thaw();
+            document.fully_activate();
             return;
         }
         let mut loads = self.incomplete_loads.borrow_mut();
@@ -1565,7 +1566,7 @@ impl ScriptThread {
     }
 
     /// Handles a request to exit a pipeline and shut down layout.
-    fn handle_exit_pipeline_msg(&self, id: PipelineId) {
+    fn handle_exit_pipeline_msg(&self, id: PipelineId, discard_bc: DiscardBrowsingContext) {
         debug!("Exiting pipeline {}.", id);
 
         self.closed_pipelines.borrow_mut().insert(id);
@@ -1591,6 +1592,11 @@ impl ScriptThread {
 
         if let Some(document) = self.documents.borrow_mut().remove(id) {
             shut_down_layout(document.window());
+            if discard_bc == DiscardBrowsingContext::Yes {
+                if let Some(context) = document.browsing_context() {
+                    context.discard();
+                }
+            }
             let _ = self.constellation_chan.send(ConstellationMsg::PipelineExited(id));
         }
 
@@ -1606,7 +1612,7 @@ impl ScriptThread {
         pipeline_ids.extend(self.documents.borrow().iter().next().map(|(pipeline_id, _)| pipeline_id));
 
         for pipeline_id in pipeline_ids {
-            self.handle_exit_pipeline_msg(pipeline_id);
+            self.handle_exit_pipeline_msg(pipeline_id, DiscardBrowsingContext::Yes);
         }
 
         debug!("Exited script thread.");
@@ -1819,9 +1825,13 @@ impl ScriptThread {
                                      referrer_policy);
         document.set_ready_state(DocumentReadyState::Loading);
 
+        if !incomplete.is_frozen {
+            document.fully_activate();
+        }
+
         self.documents.borrow_mut().insert(incomplete.pipeline_id, &*document);
 
-        browsing_context.set_active_document(&document);
+        window.init_document(&document);
 
         self.constellation_chan
             .send(ConstellationMsg::ActivateDocument(incomplete.pipeline_id))
@@ -2253,8 +2263,8 @@ fn shut_down_layout(window: &Window) {
     // Drop our references to the JSContext and DOM objects.
     window.clear_js_runtime();
 
-    // Sever the connection between the global and the DOM tree
+    // Discard the browsing context.
-    browsing_context.unset_active_document();
+    browsing_context.discard();
 
     // Destroy the layout thread. If there were node leaks, layout will now crash safely.
     chan.send(message::Msg::ExitNow).ok();

components/script_traits/lib.rs

@@ -184,6 +184,15 @@ pub struct NewLayoutInfo {
     pub layout_threads: usize,
 }
 
+/// When a pipeline is closed, should its browsing context be discarded too?
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Deserialize, Serialize)]
+pub enum DiscardBrowsingContext {
+    /// Discard the browsing context
+    Yes,
+    /// Don't discard the browsing context
+    No,
+}
+
 /// Messages sent from the constellation or layout to the script thread.
 #[derive(Deserialize, Serialize)]
 pub enum ConstellationControlMsg {
@@ -194,7 +203,7 @@ pub enum ConstellationControlMsg {
     /// Notifies script that window has been resized but to not take immediate action.
     ResizeInactive(PipelineId, WindowSizeData),
     /// Notifies the script that a pipeline should be closed.
-    ExitPipeline(PipelineId),
+    ExitPipeline(PipelineId, DiscardBrowsingContext),
     /// Notifies the script that the whole thread should be closed.
     ExitScriptThread,
     /// Sends a DOM event.

components/script_traits/script_msg.rs

@@ -102,7 +102,8 @@ pub enum ScriptMsg {
     /// Status message to be displayed in the chrome, eg. a link URL on mouseover.
     NodeStatus(Option<String>),
     /// Notification that this iframe should be removed.
-    RemoveIFrame(PipelineId, Option<IpcSender<()>>),
+    /// Returns a list of pipelines which were closed.
+    RemoveIFrame(FrameId, IpcSender<Vec<PipelineId>>),
     /// Change pipeline visibility
     SetVisible(PipelineId, bool),
     /// Notifies constellation that an iframe's visibility has been changed.

tests/wpt/metadata/MANIFEST.json

@@ -45852,6 +45852,12 @@
             "path": "cssom/overflow-serialization.html",
             "url": "/cssom/overflow-serialization.html"
           }
+        ],
+        "html/semantics/embedded-content/the-iframe-element/iframe-synchronously-discard.html": [
+          {
+            "path": "html/semantics/embedded-content/the-iframe-element/iframe-synchronously-discard.html",
+            "url": "/html/semantics/embedded-content/the-iframe-element/iframe-synchronously-discard.html"
+          }
         ]
       }
     },

tests/wpt/web-platform-tests/html/semantics/embedded-content/the-iframe-element/iframe-synchronously-discard.html

@@ -0,0 +1,32 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>IFrame discards are processed synchronously</title>
+<body></body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  async_test(function(t) {
+    var child = document.createElement("iframe");
+    child.src = "support/blank.htm?1";
+    child.onload = t.step_func(function () {
+      var childWindow = child.contentWindow;
+      var grandchild = childWindow.document.createElement("iframe");
+      grandchild.src = "blank.htm?2";
+      grandchild.onload = t.step_func(function () {
+        var grandchildWindow = grandchild.contentWindow;
+        assert_equals(child.contentWindow, childWindow, "child window");
+        assert_equals(childWindow.parent, window, "child parentage");
+        assert_equals(grandchild.contentWindow, grandchildWindow, "grandchild window");
+        assert_equals(grandchildWindow.parent, childWindow, "grandchild parentage");
+        document.body.removeChild(child);
+        assert_equals(child.contentWindow, null, "child should be discarded");
+        assert_equals(childWindow.parent, null, "child window should be discarded");
+        assert_equals(grandchild.contentWindow, null, "grandchild should be discarded");
+        assert_equals(grandchildWindow.parent, null, "grandchild window should be discarded");
+        t.done();
+      });
+      childWindow.document.body.appendChild(grandchild);
+    });
+    document.body.appendChild(child);
+  });
+</script>