Add support for onvoiceschanged event.

Source/modules/speech/SpeechSynthesis.cpp

 /*
  * Copyright (C) 2013 Apple 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 16 matching lines @@
 #include "modules/speech/SpeechSynthesis.h"
 
 #include "core/platform/PlatformSpeechSynthesisVoice.h"
 #include "core/platform/PlatformSpeechSynthesizer.h"
 #include "modules/speech/SpeechSynthesisEvent.h"
 #include "modules/speech/SpeechSynthesisUtterance.h"
 #include "wtf/CurrentTime.h"
 
 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)
 {
     ScriptWrappable::init(this);
 }
 
 void SpeechSynthesis::setPlatformSynthesizer(PassOwnPtr<PlatformSpeechSynthesizer> synthesizer)
 {
     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()
 {
     if (m_voiceList.size())
         return m_voiceList;
 
     // If the voiceList is empty, that's the cue to get the voices from the platform again.
     const Vector<RefPtr<PlatformSpeechSynthesisVoice> >& platformVoices = m_platformSpeechSynthesizer->voiceList();
     size_t voiceCount = platformVoices.size();
@@ skipping 133 matching lines @@
     if (utterance->client())
         handleSpeakingCompleted(static_cast<SpeechSynthesisUtterance*>(utterance->client()), false);
 }
 
 void SpeechSynthesis::speakingErrorOccurred(PassRefPtr<PlatformSpeechSynthesisUtterance> utterance)
 {
     if (utterance->client())
         handleSpeakingCompleted(static_cast<SpeechSynthesisUtterance*>(utterance->client()), true);
 }
 
+const AtomicString& SpeechSynthesis::interfaceName() const
+{
+    return EventTargetNames::SpeechSynthesisUtterance;
+}
+
 } // namespace WebCore