2011-04-05 Chris Rogers <crogers@google.com>

      Reviewed by Kenneth Russell.

        Add support for offline audio rendering to AudioContext API
        https://bugs.webkit.org/show_bug.cgi?id=57676

        No new tests since audio API is not yet implemented.

        * DerivedSources.make:
        * WebCore.gypi:
        * WebCore.xcodeproj/project.pbxproj:
        * bindings/js/JSAudioContextCustom.cpp:
        (WebCore::JSAudioContextConstructor::constructJSAudioContext):
        * bindings/js/JSEventCustom.cpp:
        (WebCore::toJS):
        * bindings/js/JSEventTarget.cpp:
        (WebCore::toJS):
        * bindings/v8/V8DOMWrapper.cpp:
        (WebCore::V8DOMWrapper::convertEventTargetToV8Object):
        * bindings/v8/custom/V8AudioContextCustom.cpp:
        (WebCore::V8AudioContext::constructorCallback):
        * bindings/v8/custom/V8EventCustom.cpp:
        (WebCore::toV8):
        * dom/Event.cpp:
        (WebCore::Event::isOfflineAudioCompletionEvent):
        * dom/Event.h:
        * dom/EventTarget.cpp:
        (WebCore::EventTarget::toAudioContext):
        * dom/EventTarget.h:
        * platform/audio/HRTFDatabaseLoader.cpp:
        (WebCore::HRTFDatabaseLoader::waitForLoaderThreadCompletion):
        * platform/audio/HRTFDatabaseLoader.h:
        (WebCore::HRTFDatabaseLoader::loader):
        * webaudio/AudioContext.cpp:
        (WebCore::AudioContext::createOfflineContext):
        (WebCore::AudioContext::AudioContext):
        (WebCore::AudioContext::constructCommon):
        (WebCore::AudioContext::document):
        (WebCore::AudioContext::scriptExecutionContext):
        (WebCore::AudioContext::toAudioContext):
        (WebCore::AudioContext::startRendering):
        (WebCore::AudioContext::fireCompletionEvent):
        * webaudio/AudioContext.h:
        (WebCore::AudioContext::isOfflineContext):
        (WebCore::AudioContext::eventTargetData):
        (WebCore::AudioContext::ensureEventTargetData):
        (WebCore::AudioContext::r