Properly insert text in document when parsing

If the last child of a node is a Text child and we are inserting text in that node,
we need to append it to that Text child. Doing that means that
HTMLStyleElement::children_changed gets called less frequently, but that's not a
problem during parsing thanks to the pop hook.

components/script/dom/htmlstyleelement.rs

@@ -36,6 +36,7 @@ pub struct HTMLStyleElement {
     cssom_stylesheet: MutNullableJS<CSSStyleSheet>,
     /// https://html.spec.whatwg.org/multipage/#a-style-sheet-that-is-blocking-scripts
     parser_inserted: Cell<bool>,
+    in_stack_of_open_elements: Cell<bool>,
     pending_loads: Cell<u32>,
     any_failed_load: Cell<bool>,
 }
@@ -50,6 +51,7 @@ impl HTMLStyleElement {
             stylesheet: DOMRefCell::new(None),
             cssom_stylesheet: MutNullableJS::new(None),
             parser_inserted: Cell::new(creator == ElementCreator::ParserCreated),
+            in_stack_of_open_elements: Cell::new(creator == ElementCreator::ParserCreated),
             pending_loads: Cell::new(0),
             any_failed_load: Cell::new(false),
         }
@@ -124,20 +126,38 @@ impl VirtualMethods for HTMLStyleElement {
     }
 
     fn children_changed(&self, mutation: &ChildrenMutation) {
-        if let Some(ref s) = self.super_type() {
-            s.children_changed(mutation);
-        }
-        if self.upcast::<Node>().is_in_doc() {
+        self.super_type().unwrap().children_changed(mutation);
+
+        // https://html.spec.whatwg.org/multipage/#update-a-style-block
+        // Handles the case when:
+        // "The element is not on the stack of open elements of an HTML parser or XML parser,
+        // and one of its child nodes is modified by a script."
+        // TODO: Handle Text child contents being mutated.
+        if self.upcast::<Node>().is_in_doc() && !self.in_stack_of_open_elements.get() {
             self.parse_own_css();
         }
     }
 
     fn bind_to_tree(&self, tree_in_doc: bool) {
-        if let Some(ref s) = self.super_type() {
-            s.bind_to_tree(tree_in_doc);
-        }
+        self.super_type().unwrap().bind_to_tree(tree_in_doc);
 
-        if tree_in_doc {
+        // https://html.spec.whatwg.org/multipage/#update-a-style-block
+        // Handles the case when:
+        // "The element is not on the stack of open elements of an HTML parser or XML parser,
+        // and it becomes connected or disconnected."
+        if tree_in_doc && !self.in_stack_of_open_elements.get() {
+            self.parse_own_css();
+        }
+    }
+
+    fn pop(&self) {
+        self.super_type().unwrap().pop();
+
+        // https://html.spec.whatwg.org/multipage/#update-a-style-block
+        // Handles the case when:
+        // "The element is popped off the stack of open elements of an HTML parser or XML parser."
+        self.in_stack_of_open_elements.set(false);
+        if self.upcast::<Node>().is_in_doc() {
             self.parse_own_css();
         }
     }

components/script/dom/htmltextareaelement.rs

@@ -425,6 +425,13 @@ impl VirtualMethods for HTMLTextAreaElement {
             }
         }
     }
+
+    fn pop(&self) {
+        self.super_type().unwrap().pop();
+
+        // https://html.spec.whatwg.org/multipage/#the-textarea-element:stack-of-open-elements
+        self.reset();
+    }
 }
 
 impl FormControl for HTMLTextAreaElement {}

components/script/dom/servoparser/html.rs

@@ -20,6 +20,7 @@ use dom::htmltemplateelement::HTMLTemplateElement;
 use dom::node::Node;
 use dom::processinginstruction::ProcessingInstruction;
 use dom::text::Text;
+use dom::virtualmethods::vtable_for;
 use html5ever::Attribute;
 use html5ever::serialize::{AttrRef, Serializable, Serializer};
 use html5ever::serialize::TraversalScope;
@@ -124,7 +125,7 @@ struct Sink {
     document: JS<Document>,
 }
 
-impl<'a> TreeSink for Sink {
+impl TreeSink for Sink {
     type Output = Self;
     fn finish(self) -> Self { self }
 
@@ -233,7 +234,11 @@ impl<'a> TreeSink for Sink {
         while let Some(ref child) = node.GetFirstChild() {
             new_parent.AppendChild(&child).unwrap();
         }
+    }
 
+    fn pop(&mut self, node: JS<Node>) {
+        let node = Root::from_ref(&*node);
+        vtable_for(&node).pop();
     }
 }
 
@@ -243,10 +248,13 @@ fn insert(parent: &Node, reference_child: Option<&Node>, child: NodeOrText<JS<No
             assert!(parent.InsertBefore(&n, reference_child).is_ok());
         },
         NodeOrText::AppendText(t) => {
-            // FIXME(ajeffrey): convert directly from tendrils to DOMStrings
-            let s: String = t.into();
-            let text = Text::new(DOMString::from(s), &parent.owner_doc());
-            assert!(parent.InsertBefore(text.upcast(), reference_child).is_ok());
+            if let Some(text) = parent.GetLastChild().and_then(Root::downcast::<Text>) {
+                text.upcast::<CharacterData>().append_data(&t);
+            } else {
+                let s: String = t.into();
+                let text = Text::new(DOMString::from(s), &parent.owner_doc());
+                parent.InsertBefore(text.upcast(), reference_child).unwrap();
+            }
         }
     }
 }

components/script/dom/servoparser/xml.rs

@@ -17,6 +17,7 @@ use dom::htmlscriptelement::HTMLScriptElement;
 use dom::node::Node;
 use dom::processinginstruction::ProcessingInstruction;
 use dom::text::Text;
+use dom::virtualmethods::vtable_for;
 use html5ever::tokenizer::buffer_queue::BufferQueue;
 use html5ever_atoms::{Prefix, QualName};
 use js::jsapi::JSTracer;
@@ -196,4 +197,9 @@ impl TreeSink for Sink {
             NextParserState::Continue
         }
     }
+
+    fn pop(&mut self, node: Self::Handle) {
+        let node = Root::from_ref(&*node);
+        vtable_for(&node).pop();
+    }
 }

components/script/dom/virtualmethods.rs

@@ -124,6 +124,14 @@ pub trait VirtualMethods {
             s.cloning_steps(copy, maybe_doc, clone_children);
         }
     }
+
+    /// Called on an element when it is popped off the stack of open elements
+    /// of a parser.
+    fn pop(&self) {
+        if let Some(ref s) = self.super_type() {
+            s.pop();
+        }
+    }
 }
 
 /// Obtain a VirtualMethods instance for a given Node-derived object. Any