Invalidate the previous caret location when editing text nodes.

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.
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  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 713 matching lines @@
     LayoutViewItem view = m_frame->document()->layoutViewItem();
     if (m_previousCaretNode && (m_caretBase->shouldRepaintCaret(*m_previousCaretNode) || m_caretBase->shouldRepaintCaret(view)))
         m_caretBase->invalidateLocalCaretRect(m_previousCaretNode.get(), m_previousCaretRect);
     if (newNode && (m_caretBase->shouldRepaintCaret(*newNode) || m_caretBase->shouldRepaintCaret(view)))
         m_caretBase->invalidateLocalCaretRect(newNode, newRect);
     m_previousCaretNode = newNode;
     m_previousCaretRect = newRect;
     m_previousCaretVisibility = m_caretBase->getCaretVisibility();
 }
 
+void FrameSelection::dataWillChange(const CharacterData& node)
+{
+    if (node == m_previousCaretNode) {
+        // This invalidation is eager, and intentionally uses stale state.
+        DisableCompositingQueryAsserts disabler;
+        m_caretBase->invalidateLocalCaretRect(m_previousCaretNode.get(), m_previousCaretRect);

[yosin_UTC9, 2016/04/29 15:03:12]

Should we reset other states of previous cares like |nodeWillBeRemoved()|?
There are:
        m_caretBase->invalidateLocalCaretRect(m_previousCaretNode.get(),
m_previousCaretRect);
        m_previousCaretNode = nullptr;
        m_previousCaretRect = LayoutRect();
        m_previousCaretVisibility = CaretVisibility::Hidden;
If so, it is better to have |resetPreviousCaretStates()| or another good name to
share code.

[chrishtr, 2016/04/29 20:09:40]

I think those other changes will still be handled correctly by
nodeWillBeRemoved. If a text
node was mutated but not deleted, there is no need to zero out the caret node as
far as I
can see.

Updating m_previousCaretRect needs to happen, but that can also be done in
invalidateCaretRect() later in the lifecycle for the current frame. 

+    }
+}
+
 void FrameSelection::paintCaret(GraphicsContext& context, const LayoutPoint& paintOffset)
 {
     if (selection().isCaret() && m_shouldPaintCaret) {
         m_caretBase->updateCaretRect(PositionWithAffinity(selection().start(), selection().affinity()));
         m_caretBase->paintCaret(selection().start().anchorNode(), context, paintOffset);
     }
 }
 
 bool FrameSelection::contains(const LayoutPoint& point)
 {
@@ skipping 676 matching lines @@
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
     else
         fprintf(stderr, "Cannot showTree for (nil) FrameSelection.\n");
 }
 
 #endif