Keep AudioScheduledSourceNode alive until onended is called.

Source/modules/webaudio/AudioScheduledSourceNode.cpp

Index: Source/modules/webaudio/AudioScheduledSourceNode.cpp
diff --git a/Source/modules/webaudio/AudioScheduledSourceNode.cpp b/Source/modules/webaudio/AudioScheduledSourceNode.cpp
index c467527aff906266be38459d2e21b6b55404f3ec..bb5236f273ec7113032233a414430cdcf1447add 100644
--- a/Source/modules/webaudio/AudioScheduledSourceNode.cpp
+++ b/Source/modules/webaudio/AudioScheduledSourceNode.cpp
@@ -42,6 +42,7 @@ const double AudioScheduledSourceNode::UnknownTime = -1;
 
 AudioScheduledSourceNode::AudioScheduledSourceNode(AudioContext* context, float sampleRate)
     : AudioSourceNode(context, sampleRate)
+    , ActiveDOMObject(context->scriptExecutionContext())
     , m_playbackState(UNSCHEDULED_STATE)
     , m_startTime(0)
     , m_endTime(UnknownTime)
@@ -144,7 +145,7 @@ void AudioScheduledSourceNode::start(double when)
     m_playbackState = SCHEDULED_STATE;
 }
 
-void AudioScheduledSourceNode::stop(double when)
+void AudioScheduledSourceNode::stopNote(double when)
 {
     ASSERT(isMainThread());
     if (!(m_playbackState == SCHEDULED_STATE || m_playbackState == PLAYING_STATE))
@@ -161,7 +162,7 @@ void AudioScheduledSourceNode::noteOn(double when)
 
 void AudioScheduledSourceNode::noteOff(double when)
 {
-    stop(when);
+    stopNote(when);
 }
 
 void AudioScheduledSourceNode::setOnended(PassRefPtr<EventListener> listener, DOMWrapperWorld* isolatedWorld)
@@ -179,8 +180,10 @@ void AudioScheduledSourceNode::finish()
         context()->decrementActiveSourceCount();
     }
 
-    if (m_hasEndedListener)
+    if (m_hasEndedListener) {
+        setPendingActivity(this);

[Ken Russell (switch to Gerrit), 2013/09/09 21:30:05]

Sorry, I failed to realize this before. This can't be called here -- this code
runs on the audio thread, and ActiveDOMObject, Node, EventTarget, etc., aren't
thread-safe.

I think that we'll have to figure out some other solution. Perhaps the node
can't transition to the FINISHED state until the onended callback has been
called on the main thread.

[Ken Russell (switch to Gerrit), 2013/09/09 21:34:31]

Apologies, I think I'm wrong. AudioNode::ref is specifically thread-safe. Let's
follow up offline.

         callOnMainThread(&AudioScheduledSourceNode::notifyEndedDispatch, this);
+    }
 }
 
 void AudioScheduledSourceNode::notifyEndedDispatch(void* userData)
@@ -190,9 +193,24 @@ void AudioScheduledSourceNode::notifyEndedDispatch(void* userData)
 
 void AudioScheduledSourceNode::notifyEnded()
 {
-    RefPtr<Event> event = Event::create(eventNames().endedEvent);
-    event->setTarget(this);
-    dispatchEvent(event.get());
+    // Avoid firing the event if the document has already gone away.
+    if (context()->scriptExecutionContext()) {
+        RefPtr<Event> event = Event::create(eventNames().endedEvent);
+        event->setTarget(this);
+        dispatchEvent(event.get());
+    }
+    unsetPendingActivity(this);

[Ken Russell (switch to Gerrit), 2013/09/09 19:45:47]

This looks wrong now. What happens if we navigate away from the document, stop()
is called first, and the audio processing thread afterward finishes handling the
node and notifyEnded() is called on the main thread? As far as I can see both
unsetPendingActivity calls should be conditional. I don't know the conditions
under which notifyEnded will be called but please explain why this code is
correct.

+}
+
+ScriptExecutionContext* AudioScheduledSourceNode::scriptExecutionContext() const
+{
+    return context()->scriptExecutionContext();
+}
+
+void AudioScheduledSourceNode::stop()
+{
+    if (hasPendingActivity())
+        unsetPendingActivity(this);
 }
 
 } // namespace WebCore