Rewrite Shadow DOM distribution engine to support partial synchronous distribution for v1

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 9f42d72beea41659a076b3d91e52c246d1053caa..b931d2da0dd4f2f5cc777ccc7160675627b8c421 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -3839,6 +3839,11 @@ void Document::nodeChildrenWillBeRemoved(ContainerNode& container)
             frame->page()->dragCaretController().nodeWillBeRemoved(n);
         }
     }
+
+    if (containsV1ShadowTree()) {
+        for (Node& n : NodeTraversal::childrenOf(container))

[esprehn, 2016/05/23 06:41:00]

this traverses the whole subtree again whenever you remove a sutbree. ex. doing
document.body.removeChild() will get traversed again inside here. This should be
done inside ::removedFrom or ::childrenChanged or inside the notifyRemoved walk.

[hayato, 2016/05/24 13:23:38]

My intention to add this check code here, Document::nodeChildrenWillBeRemoved,
is to get this called only *once* per removing a subtree.

As far as I can read, Document::nodeChildrenWillBeRemoved is called from
ContainerNode::removeChildren, which is called only from Node::setTextContent or
something similar.
Let me re-check later, but it looks this is not called recursively.

+            n.checkSlotChangeBeforeRemoved();
+    }
 }
 
 void Document::nodeWillBeRemoved(Node& n)
@@ -3854,6 +3859,9 @@ void Document::nodeWillBeRemoved(Node& n)
         frame->selection().nodeWillBeRemoved(n);
         frame->page()->dragCaretController().nodeWillBeRemoved(n);
     }
+
+    if (containsV1ShadowTree())
+        n.checkSlotChangeBeforeRemoved();
 }
 
 void Document::dataWillChange(const CharacterData& characterData)