Add support for onvoiceschanged event.

Source/modules/speech/SpeechSynthesis.cpp

Index: Source/modules/speech/SpeechSynthesis.cpp
diff --git a/Source/modules/speech/SpeechSynthesis.cpp b/Source/modules/speech/SpeechSynthesis.cpp
index fb7ee0e39025f474d06301f4d402610f4d04ae66..e4f7c2980f656a36fa3dbc256956314f8735b896 100644
--- a/Source/modules/speech/SpeechSynthesis.cpp
+++ b/Source/modules/speech/SpeechSynthesis.cpp
@@ -34,13 +34,14 @@
 
 namespace WebCore {
 
-PassRefPtr<SpeechSynthesis> SpeechSynthesis::create()
+PassRefPtr<SpeechSynthesis> SpeechSynthesis::create(ExecutionContext* context)
 {
-    return adoptRef(new SpeechSynthesis());
+    return adoptRef(new SpeechSynthesis(context));
 }
 
-SpeechSynthesis::SpeechSynthesis()
-    : m_platformSpeechSynthesizer(PlatformSpeechSynthesizer::create(this))
+SpeechSynthesis::SpeechSynthesis(ExecutionContext* context)
+    : ContextLifecycleObserver(context)
+    , m_platformSpeechSynthesizer(PlatformSpeechSynthesizer::create(this))
     , m_currentSpeechUtterance(0)
     , m_isPaused(false)
 {
@@ -52,9 +53,15 @@ void SpeechSynthesis::setPlatformSynthesizer(PassOwnPtr<PlatformSpeechSynthesize
     m_platformSpeechSynthesizer = synthesizer;
 }
 
+ExecutionContext* SpeechSynthesis::executionContext() const
+{
+    return ContextLifecycleObserver::executionContext();
+}
+
 void SpeechSynthesis::voicesDidChange()

[abarth-chromium, 2013/10/16 19:25:06]

When can this function be called?  Why don't we need SpeechSynthesis to be an
ActiveDOMObject so that it keeps its JS wrapper alive?

[dmazzoni, 2013/10/16 22:09:06]

Good question.

This function is only called from the platform, in response to an IPC from the
browser, on the main event loop. So I don't think we have to worry about it
being in a weird state.

SpeechSynthesis is owned by the DOMWindow, and it doesn't have any state that
needs to be preserved if the window goes away. The global speech queue state is
kept by Chromium in the browser process; it keeps everything running smoothly
even when a window disappears.

[abarth-chromium, 2013/10/17 02:00:53]

I should write a design doc that explains how all this works in more detail. 
What you've written is almost correct, but there is one tiny detail: we need to
make sure not to dispatch any events after the DOMWindow detaches from the
Frame.  The easiest way to handle that is to check whether
executionContext()->activeDOMObjectsAreStopped() before dispatching the event.

[dmazzoni, 2013/10/17 15:28:59]

Got it, that makes sense.

I made the same change to SpeechSynthesis::fireEvent, does that look right?

 {
     m_voiceList.clear();
+    dispatchEvent(Event::create(EventTypeNames::voiceschanged));

[eseidel, 2013/10/16 06:44:53]

This will cause synchronous event dispatch, right?  Callers may have the frame
navigated or othewise things deleted out from under them.

[dmazzoni, 2013/10/16 07:08:00]

That's only a problem if the user is triggering this function, right? The only
caller of voicesDidChange is the platform, and that's only in response to IPC
messages from the browser process, handled in the main loop.

 }
 
 const Vector<RefPtr<SpeechSynthesisVoice> >& SpeechSynthesis::getVoices()
@@ -208,4 +215,9 @@ void SpeechSynthesis::speakingErrorOccurred(PassRefPtr<PlatformSpeechSynthesisUt
         handleSpeakingCompleted(static_cast<SpeechSynthesisUtterance*>(utterance->client()), true);
 }
 
+const AtomicString& SpeechSynthesis::interfaceName() const
+{
+    return EventTargetNames::SpeechSynthesisUtterance;
+}
+
 } // namespace WebCore