Make FrameCaret to utilize SynchronousMutationObserver

third_party/WebKit/Source/core/editing/FrameSelection.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 385 matching lines @@
   // being removed, the selection in the document that created the fragment
   // needs no adjustment.
   if (isNone() || !node.inActiveDocument())
     return;
 
   respondToNodeModification(
       node, removingNodeRemovesPosition(node, selection().base()),
       removingNodeRemovesPosition(node, selection().extent()),
       removingNodeRemovesPosition(node, selection().start()),
       removingNodeRemovesPosition(node, selection().end()));
-
-  m_frameCaret->nodeWillBeRemoved(node);

[yoichio, 2017/01/20 08:44:00]

I'm afraid if there is race condition between  
FrameSelection::nodeWillBeRemoved and FrameCaret::nodeWillBeRemoved.

I think this kind of observer implementers should not depend on each
 other because order of nodeWilleBeRemoved call is not guaranteed.
respondToNodeModification calls m_Frame functions, is that O.K?

How about documentDetached listener?

[yosin_UTC9, 2017/01/20 08:49:14]

|FrameCaret::nodeWillBeRemoved()| doesn't access |FrameSelection| and there is
no back pointer to |FrameCaret| to |FrameSelection|. So, they are mutually
exclusive.

This is one of the requirements of utilizing SMO.
|SMO::contextDestroyed()| replaces |FrameCaret::documentDetached()|.
|documentDetached()| is an old protocol between |FrameSeleciton| and
|FrameCaret|.

 }
 
 static SelectionState selectionStateOf(const Node& node) {
   const LayoutObject* layoutObject = node.layoutObject();
   if (!layoutObject)
     return SelectionNone;
   return layoutObject->getSelectionState();
 }
 
 void FrameSelection::respondToNodeModification(Node& node,
@@ skipping 44 matching lines @@
     clearLayoutTreeSelection = true;
   }
 
   if (clearLayoutTreeSelection)
     selection().start().document()->layoutViewItem().clearSelection();
 
   if (clearDOMTreeSelection)
     setSelection(SelectionInDOMTree(), DoNotSetFocus);
   m_frameCaret->setCaretRectNeedsUpdate();
 
   // TODO(yosin): We should move to call |TypingCommand::closeTyping()| to

[Xiaocheng, 2017/01/20 08:56:53]

Is this OK?

Do we need to cleanup the access from FrameSelection to FrameCaret in
FrameSelections's mutation listeners, and move them to FrameCaret's own
listeners?

[yosin_UTC9, 2017/01/20 09:09:39]

Multiple calls of FrameCaret::setCaretRectNeedsUpdate() is OK.

void FrameCaret::setCaretRectNeedsUpdate() {
  if (m_caretRectDirty)
    return;
  m_caretRectDirty = true;
...
}

If you mention about |TypingCommand::closeTyping()|, it updates
|FrameSelection|'s state and is not related to FrameCaret.
[1] make FrameSelection to utiulize SMO

[1] http://crrev.com/2638423005: Make FrameSelection to utilize
SynchronousMutationObserver

   // |Editor| class.
   if (!document().isRunningExecCommand())
     TypingCommand::closeTyping(m_frame);
 }
 
 static Position updatePositionAfterAdoptingTextReplacement(
     const Position& position,
     CharacterData* node,
     unsigned offset,
     unsigned oldLength,
@@ skipping 221 matching lines @@
     m_granularityStrategy->Clear();
   setSelection(SelectionInDOMTree());
 }
 
 void FrameSelection::documentAttached(Document* document) {
   DCHECK(document);
   DCHECK(!m_document) << "FrameSelection is already attached to " << m_document;
   m_document = document;
   m_useSecureKeyboardEntryWhenActive = false;
   m_selectionEditor->documentAttached(document);
+  m_frameCaret->documentAttached(document);
 }
 
 void FrameSelection::documentDetached(const Document& document) {
   DCHECK_EQ(m_document, document);
   m_document = nullptr;
   m_granularity = CharacterGranularity;
 
   LayoutViewItem view = m_frame->contentLayoutItem();
   if (!view.isNull())
     view.clearSelection();
 
   clearTypingStyle();
   m_selectionEditor->documentDetached(document);
-  m_frameCaret->documentDetached();
 }
 
 LayoutBlock* FrameSelection::caretLayoutObject() const {
   DCHECK(selection().isValidFor(document()));
   if (!isCaret())
     return nullptr;
   return CaretBase::caretLayoutObject(selection().start().anchorNode());
 }
 
 IntRect FrameSelection::absoluteCaretBounds() {
@@ skipping 683 matching lines @@
 }
 
 void showTree(const blink::FrameSelection* sel) {
   if (sel)
     sel->showTreeForThis();
   else
     LOG(INFO) << "Cannot showTree for <null> FrameSelection.";
 }
 
 #endif