Have WebFrameClient::suddenTerminationDisablerChanged return a boolean

Source/core/loader/FrameLoaderClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 210 matching lines @@
         virtual PassOwnPtr<blink::WebApplicationCacheHost> createApplicationCacheHost(blink::WebApplicationCacheHostClient*) = 0;
 
         virtual void didStopAllLoaders() { }
 
         virtual void dispatchDidChangeManifest() { }
 
         virtual unsigned backForwardLength() { return 0; }
 
         virtual bool isFrameLoaderClientImpl() const { return false; }
 
-        // Called when an element preventing the sudden termination of the frame
-        // is added or removed. |variation| is the number of elements added, or
-        // removed if it is negative. |type| is the type of element
+        // 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) { }
 
     };
 
 } // namespace blink
 
 #endif // FrameLoaderClient_h