script: Remove note_rendering_opportunity and rendering_opportunity (#34575)

A rendering opportunity is now unconditionally triggered by handling IPC
messages in the `ScriptThread`, unless animations are running in which
case it's driven by the compositor. We can now remove calls to
`note_rendering_opportunity` and `rendering_opportunity`.

There is one tricky case, which is when a promise completion during a
microtask checkpoint dirties the page again. In this case we need to
trigger a new rendering opportunity, unless animations are running.  In
a followup change, when not driven by the compositor, rendering
opportunities will be driven by a timed task, meaning we can remove this
workaround.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/dom/document.rs

@@ -2064,6 +2064,12 @@ impl Document {
         }
     }
 
+    /// Whether or not this `Document` has any active requestAnimationFrame callbacks
+    /// registered.
+    pub(crate) fn has_active_request_animation_frame_callbacks(&self) -> bool {
+        !self.animation_frame_list.borrow().is_empty()
+    }
+
     /// <https://html.spec.whatwg.org/multipage/#dom-window-requestanimationframe>
     pub(crate) fn request_animation_frame(&self, callback: AnimationFrameCallback) -> u32 {
         let ident = self.animation_frame_ident.get() + 1;

components/script/dom/node.rs

@@ -2129,8 +2129,6 @@ impl Node {
             MutationObserver::queue_a_mutation_record(parent, mutation);
         }
         node.owner_doc().remove_script_and_layout_blocker();
-
-        ScriptThread::note_rendering_opportunity(window_from_node(parent).pipeline_id());
     }
 
     /// <https://dom.spec.whatwg.org/#concept-node-replace-all>
@@ -2254,7 +2252,6 @@ impl Node {
             MutationObserver::queue_a_mutation_record(parent, mutation);
         }
         parent.owner_doc().remove_script_and_layout_blocker();
-        ScriptThread::note_rendering_opportunity(window_from_node(parent).pipeline_id());
     }
 
     /// <https://dom.spec.whatwg.org/#concept-node-clone>

components/script/dom/resizeobserver.rs

@@ -26,7 +26,6 @@ use crate::dom::resizeobserverentry::ResizeObserverEntry;
 use crate::dom::resizeobserversize::{ResizeObserverSize, ResizeObserverSizeImpl};
 use crate::dom::window::Window;
 use crate::script_runtime::CanGc;
-use crate::script_thread::ScriptThread;
 
 /// <https://drafts.csswg.org/resize-observer/#calculate-depth-for-node>
 #[derive(Debug, Default, PartialEq, PartialOrd)]
@@ -191,10 +190,6 @@ impl ResizeObserverMethods<crate::DomTypeHolder> for ResizeObserver {
         self.observation_targets
             .borrow_mut()
             .push((resize_observation, Dom::from_ref(target)));
-
-        // Note: noting a rendering opportunity here is necessary
-        // to make /resize-observer/iframe-same-origin.html PASS.
-        ScriptThread::note_rendering_opportunity(window_from_node(target).pipeline_id());
     }
 
     /// <https://drafts.csswg.org/resize-observer/#dom-resizeobserver-unobserve>

components/script/dom/window.rs

@@ -1809,6 +1809,10 @@ impl Window {
         ScriptThread::handle_tick_all_animations_for_testing(pipeline_id);
     }
 
+    pub(crate) fn reflows_suppressed(&self) -> bool {
+        self.suppress_reflow.get()
+    }
+
     /// Reflows the page unconditionally if possible and not suppressed. This method will wait for
     /// the layout to complete. If there is no window size yet, the page is presumed invisible and
     /// no reflow is performed. If reflow is suppressed, no reflow will be performed for ForDisplay