updating Input field value by script should reset IME composition.

third_party/WebKit/public/web/WebViewClient.h

 /*
  * Copyright (C) 2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 149 matching lines @@
 
   // Take focus away from the WebView by focusing an adjacent UI element
   // in the containing window.
   virtual void FocusNext() {}
   virtual void FocusPrevious() {}
 
   // Called when a new node gets focused. |fromNode| is the previously focused
   // node, |toNode| is the newly focused node. Either can be null.
   virtual void FocusedNodeChanged(const WebNode& from_node,
                                   const WebNode& to_node) {}
+  virtual void DidCancelCompositionOnSelectionChange() {}
 
   // Called to check if layout update should be processed.
   virtual bool CanUpdateLayout() { return false; }
 
   // Indicates two things:
   //   1) This view may have a new layout now.
   //   2) Calling layout() is a no-op.
   // After calling WebWidget::layout(), expect to get this notification
   // unless the view did not need a layout.
   virtual void DidUpdateLayout() {}
@@ skipping 86 matching lines @@
                                   bool page_changed) override {}
   void Show(WebNavigationPolicy) override {}
   virtual WebWidgetClient* WidgetClient() { return this; }
 
  protected:
 };
 
 }  // namespace blink
 
 #endif