Keep the selection of the text field when changed by JS.

Source/core/editing/FrameSelection.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 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 235 matching lines @@
     VisiblePosition modifyMovingForward(TextGranularity);
     VisiblePosition modifyExtendingLeft(TextGranularity);
     VisiblePosition modifyExtendingBackward(TextGranularity);
     VisiblePosition modifyMovingLeft(TextGranularity);
     VisiblePosition modifyMovingBackward(TextGranularity);
 
     LayoutUnit lineDirectionPointForBlockDirectionNavigation(EPositionType);
 
     void notifyAccessibilityForSelectionChange();
     void notifyCompositorForSelectionChange();
+    void notifyEventHandlerForSelectionChange();
 
     void focusedOrActiveStateChanged();
 
     void caretBlinkTimerFired(Timer<FrameSelection>*);
 
     void setUseSecureKeyboardEntry(bool);
 
     void setCaretVisibility(CaretVisibility);
     bool shouldBlinkCaret() const;
 
@@ skipping 50 matching lines @@
 }
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const blink::FrameSelection&);
 void showTree(const blink::FrameSelection*);
 #endif
 
 #endif // FrameSelection_h