Make non-null VisibleSelections creatable only by createVisibleSelection[Deprecated]

third_party/WebKit/Source/modules/accessibility/AXLayoutObject.cpp

 /*
 * Copyright (C) 2008 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
@@ skipping 1897 matching lines @@
     // This callsite should probably move up the stack.
     frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();
 
     // Set the selection based on visible positions, because the offsets in accessibility nodes
     // are based on visible indexes, which often skips redundant whitespace, for example.
     VisiblePosition anchorVisiblePosition = toVisiblePosition(anchorObject, selection.anchorOffset);
     VisiblePosition focusVisiblePosition = toVisiblePosition(focusObject, selection.focusOffset);
     if (anchorVisiblePosition.isNull() || focusVisiblePosition.isNull())
         return;
 
-    frame->selection().setSelection(VisibleSelection(anchorVisiblePosition, focusVisiblePosition));
+    frame->selection().setSelection(createVisibleSelection(anchorVisiblePosition, focusVisiblePosition));

[yosin_UTC9, 2016/09/30 01:20:35]

Since AXLayoutObject holds |m_layoutObject|, when |VisibleSelection| ctor causes
layout and blow up this AXLayoutObject.
So, this change declare |createVisibleSlection()| don't cause layout.
Nice!

 }
 
 bool AXLayoutObject::isValidSelectionBound(const AXObject* boundObject) const
 {
     return getLayoutObject() && boundObject && !boundObject->isDetached()
         && boundObject->isAXLayoutObject() && boundObject->getLayoutObject()
         && boundObject->getLayoutObject()->frame() == getLayoutObject()->frame()
         && &boundObject->axObjectCache() == &axObjectCache();
 }
 
@@ skipping 465 matching lines @@
 
 bool AXLayoutObject::elementAttributeValue(const QualifiedName& attributeName) const
 {
     if (!m_layoutObject)
         return false;
 
     return equalIgnoringCase(getAttribute(attributeName), "true");
 }
 
 } // namespace blink