Have WebFrameClient::suddenTerminationDisablerChanged return a boolean

public/web/WebFrameClient.h

 /*
  * Copyright (C) 2011, 2012 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 599 matching lines @@
     // Similarly, when exitFullScreen is called,
     // WebWidget::{will,Did}ExitFullScreen should bound resizing the WebWidget
     // out of fullscreen mode.
     // Note: the return value is ignored.
     virtual bool enterFullscreen() { return false; }
     virtual bool exitFullscreen() { return false; }
 
 
     // Sudden termination --------------------------------------------------
 
-    // Called when an element preventing the sudden termination of the frame is
-    // added or removed. |variation| is the number of elements added, removed if
-    // it is negative. |type| is the type of element (BeforeUnload handler,
-    // Unload handler).
+    // Called when elements preventing the sudden termination of the frame
+    // become present or stop being present. |type| is the type of element
+    // (BeforeUnload handler, Unload handler).
     enum SuddenTerminationDisablerType {
         BeforeUnloadHandler,
         UnloadHandler,
     };
-    virtual void suddenTerminationDisablerChanged(int variation, SuddenTerminationDisablerType) { }
+    virtual void suddenTerminationDisablerChanged(bool present, SuddenTerminationDisablerType) { }
 
 protected:
     virtual ~WebFrameClient() { }
 };
 
 } // namespace blink
 
 #endif