Simplify invokeCallback() and support void return values for IDL callbacks

Source/modules/filesystem/SyncCallbackHelper.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2013 Samsung Electronics. 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.
@@ skipping 93 matching lines @@
     PassOwnPtr<ErrorCallback> errorCallback() { return ErrorCallbackImpl::create(this); }
 
 private:
     class SuccessCallbackImpl : public SuccessCallback {
     public:
         static PassOwnPtr<SuccessCallbackImpl> create(HelperType* helper)
         {
             return adoptPtr(new SuccessCallbackImpl(helper));
         }
 
-        virtual bool handleEvent()
+        virtual void handleEvent()
         {
             m_helper->setError(FileError::OK);
-            return true;
         }
 
-        virtual bool handleEvent(CallbackArg arg)
+        virtual void handleEvent(CallbackArg arg)
         {
             m_helper->setResult(arg);
-            return true;
         }
 
     private:
         explicit SuccessCallbackImpl(HelperType* helper)
             : m_helper(helper)
         {
         }
         HelperType* m_helper;
     };
 
     class ErrorCallbackImpl : public ErrorCallback {
     public:
         static PassOwnPtr<ErrorCallbackImpl> create(HelperType* helper)
         {
             return adoptPtr(new ErrorCallbackImpl(helper));
         }
 
-        virtual bool handleEvent(FileError* error)
+        virtual void handleEvent(FileError* error)
         {
             ASSERT(error);
             m_helper->setError(error->code());
-            return true;
         }
 
     private:
         explicit ErrorCallbackImpl(HelperType* helper)
             : m_helper(helper)
         {
         }
         HelperType* m_helper;
     };
 
@@ skipping 23 matching lines @@
 
 typedef SyncCallbackHelper<EntryCallback, Entry*, EntrySync> EntrySyncCallbackHelper;
 typedef SyncCallbackHelper<EntriesCallback, const EntryVector&, EntrySyncVector> EntriesSyncCallbackHelper;
 typedef SyncCallbackHelper<MetadataCallback, Metadata*, Metadata> MetadataSyncCallbackHelper;
 typedef SyncCallbackHelper<VoidCallback, EmptyType*, EmptyType> VoidSyncCallbackHelper;
 typedef SyncCallbackHelper<FileSystemCallback, DOMFileSystem*, DOMFileSystemSync> FileSystemSyncCallbackHelper;
 
 } // namespace WebCore
 
 #endif // SyncCallbackHelper_h