Avoid using cross RenderView selection rendering

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 1568 matching lines @@
     Position endPos = selection.end();
     candidate = endPos.upstream();
     if (candidate.isCandidate())
         endPos = candidate;
 
     // We can get into a state where the selection endpoints map to the same VisiblePosition when a selection is deleted
     // because we don't yet notify the FrameSelection of text removal.
     if (startPos.isNotNull() && endPos.isNotNull() && selection.visibleStart() != selection.visibleEnd()) {
         RenderObject* startRenderer = startPos.deprecatedNode()->renderer();
         RenderObject* endRenderer = endPos.deprecatedNode()->renderer();
-        view->setSelection(startRenderer, startPos.deprecatedEditingOffset(), endRenderer, endPos.deprecatedEditingOffset());
+        if (startRenderer->view() == view && endRenderer->view() == view)

[Yuta Kitamura, 2014/04/14 06:23:40]

This line would probably deserve some comments because it's not very obvious
why we need these checks.

[yosin_UTC9, 2014/04/14 08:03:56]

Done.

+            view->setSelection(startRenderer, startPos.deprecatedEditingOffset(), endRenderer, endPos.deprecatedEditingOffset());
     }
 }
 
 void FrameSelection::setCaretVisibility(CaretVisibility visibility)
 {
     if (caretVisibility() == visibility)
         return;
 
     m_frame->document()->updateLayoutIgnorePendingStylesheets();
     if (m_caretPaint) {
@@ skipping 276 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const WebCore::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif