Move the exception logic to the AudioNode creator

third_party/WebKit/Source/modules/webaudio/MediaStreamAudioSourceNode.cpp

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 #include "modules/webaudio/MediaStreamAudioSourceNode.h"
+
+#include "core/dom/ExceptionCode.h"
 #include "modules/webaudio/AbstractAudioContext.h"
 #include "modules/webaudio/AudioNodeOutput.h"
 #include "platform/Logging.h"
 #include "wtf/Locker.h"
 
 namespace blink {
 
 MediaStreamAudioSourceHandler::MediaStreamAudioSourceHandler(AudioNode& node, MediaStream& mediaStream, MediaStreamTrack* audioTrack, PassOwnPtr<AudioSourceProvider> audioSourceProvider)
     : AudioHandler(NodeTypeMediaStreamAudioSource, node, node.context()->sampleRate())
     , m_mediaStream(mediaStream)
@@ skipping 71 matching lines @@
 }
 
 // ----------------------------------------------------------------
 
 MediaStreamAudioSourceNode::MediaStreamAudioSourceNode(AbstractAudioContext& context, MediaStream& mediaStream, MediaStreamTrack* audioTrack, PassOwnPtr<AudioSourceProvider> audioSourceProvider)
     : AudioSourceNode(context)
 {
     setHandler(MediaStreamAudioSourceHandler::create(*this, mediaStream, audioTrack, std::move(audioSourceProvider)));
 }
 
-MediaStreamAudioSourceNode* MediaStreamAudioSourceNode::create(AbstractAudioContext& context, MediaStream& mediaStream, MediaStreamTrack* audioTrack, PassOwnPtr<AudioSourceProvider> audioSourceProvider)
+MediaStreamAudioSourceNode* MediaStreamAudioSourceNode::create(AbstractAudioContext& context, MediaStream& mediaStream, ExceptionState& exceptionState)
 {
-    return new MediaStreamAudioSourceNode(context, mediaStream, audioTrack, std::move(audioSourceProvider));
+    DCHECK(isMainThread());
+
+    if (context.isContextClosed()) {
+        context.throwExceptionForClosedState(exceptionState);
+        return nullptr;
+    }
+
+    MediaStreamTrackVector audioTracks = mediaStream.getAudioTracks();
+    if (audioTracks.isEmpty()) {
+        exceptionState.throwDOMException(
+            InvalidStateError,
+            "MediaStream has no audio track");
+        return nullptr;
+    }
+
+    // Use the first audio track in the media stream.
+    MediaStreamTrack* audioTrack = audioTracks[0];
+    OwnPtr<AudioSourceProvider> provider = audioTrack->createWebAudioSource();
+
+    MediaStreamAudioSourceNode* node = new MediaStreamAudioSourceNode(context, mediaStream, audioTrack, provider.release());
+
+    if (!node)
+        return nullptr;
+
+    // TODO(hongchan): Only stereo streams are supported right now. We should be able to accept

[hongchan, 2016/05/20 21:28:32]

I think we agreed to wrap the comment at 80 cols.

+    // multi-channel streams.
+    node->setFormat(2, context.sampleRate());
+    // context keeps reference until node is disconnected
+    context.notifySourceNodeStartedProcessing(node);
+
+    return node;
 }
 
 DEFINE_TRACE(MediaStreamAudioSourceNode)
 {
     AudioSourceProviderClient::trace(visitor);
     AudioSourceNode::trace(visitor);
 }
 
 MediaStreamAudioSourceHandler& MediaStreamAudioSourceNode::mediaStreamAudioSourceHandler() const
 {
     return static_cast<MediaStreamAudioSourceHandler&>(handler());
 }
 
 MediaStream* MediaStreamAudioSourceNode::getMediaStream() const
 {
     return mediaStreamAudioSourceHandler().getMediaStream();
 }
 
 void MediaStreamAudioSourceNode::setFormat(size_t numberOfChannels, float sourceSampleRate)
 {
     mediaStreamAudioSourceHandler().setFormat(numberOfChannels, sourceSampleRate);
 }
 
 } // namespace blink