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

Source/modules/filesystem/DOMFileSystem.cpp

 /*
  * Copyright (C) 2010 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 103 matching lines @@
 
 namespace {
 
 class ConvertToFileWriterCallback : public FileWriterBaseCallback {
 public:
     static PassOwnPtr<ConvertToFileWriterCallback> create(PassOwnPtr<FileWriterCallback> callback)
     {
         return adoptPtr(new ConvertToFileWriterCallback(callback));
     }
 
-    bool handleEvent(FileWriterBase* fileWriterBase)
+    void handleEvent(FileWriterBase* fileWriterBase)
     {
-        return m_callback->handleEvent(static_cast<FileWriter*>(fileWriterBase));
+        m_callback->handleEvent(static_cast<FileWriter*>(fileWriterBase));
     }
 private:
     ConvertToFileWriterCallback(PassOwnPtr<FileWriterCallback> callback)
         : m_callback(callback)
     {
     }
     OwnPtr<FileWriterCallback> m_callback;
 };
 
 }
@@ skipping 60 matching lines @@
 
 } // namespace
 
 void DOMFileSystem::createFile(const FileEntry* fileEntry, PassOwnPtr<FileCallback> successCallback, PassOwnPtr<ErrorCallback> errorCallback)
 {
     KURL fileSystemURL = createFileSystemURL(fileEntry);
     fileSystem()->createSnapshotFileAndReadMetadata(fileSystemURL, SnapshotFileCallback::create(this, fileEntry->name(), fileSystemURL, successCallback, errorCallback));
 }
 
 } // namespace WebCore