b=967992 collect unreferenced AudioBufferSourceNodes with no buffer r=padenot

The playing ref now only exists while there is a buffer.
We don't currently dispatch ended events when there is no buffer.

--HG--
extra : transplant_source : Ba%0BRD%89%96%99%F14%B6%40%3D%B2%C1%D5%28%D6%15%12

content/media/webaudio/AudioBufferSourceNode.cpp

@@ -537,8 +537,6 @@ AudioBufferSourceNode::Start(double aWhen, double aOffset,
   if (aWhen > 0.0) {
     ns->SetStreamTimeParameter(START, Context(), aWhen);
   }
-
-  MarkActive();
 }
 
 void
@@ -559,6 +557,8 @@ AudioBufferSourceNode::SendBufferParameterToStream(JSContext* aCx)
     }
   } else {
     ns->SetBuffer(nullptr);
+
+    MarkInactive();
   }
 }
 
@@ -582,6 +582,8 @@ AudioBufferSourceNode::SendOffsetAndDurationParametersToStream(AudioNodeStream*
                          offsetSamples + NS_lround(mDuration * rate));
   }
   aStream->SetInt32Parameter(BUFFEREND, bufferEnd);
+
+  MarkActive();
 }
 
 void
@@ -597,12 +599,6 @@ AudioBufferSourceNode::Stop(double aWhen, ErrorResult& aRv)
     return;
   }
 
-  if (!mBuffer) {
-    // We don't have a buffer, so the stream is never marked as finished.
-    // Therefore we need to drop our playing ref right now.
-    MarkInactive();
-  }
-
   AudioNodeStream* ns = static_cast<AudioNodeStream*>(mStream.get());
   if (!ns || !Context()) {
     // We've already stopped and had our stream shut down