MediaRecorder: make EventListener and stop if receiving on{add,remove}track from WebMediaStream

third_party/WebKit/Source/modules/mediarecorder/MediaRecorder.cpp

Index: third_party/WebKit/Source/modules/mediarecorder/MediaRecorder.cpp
diff --git a/third_party/WebKit/Source/modules/mediarecorder/MediaRecorder.cpp b/third_party/WebKit/Source/modules/mediarecorder/MediaRecorder.cpp
index 9713746b3413c61ba99626773af403ac7249b3eb..98974732a7f778d09cc99b766fe2d16a27afbc4f 100644
--- a/third_party/WebKit/Source/modules/mediarecorder/MediaRecorder.cpp
+++ b/third_party/WebKit/Source/modules/mediarecorder/MediaRecorder.cpp
@@ -36,6 +36,33 @@ String stateToString(MediaRecorder::State state)
 
 } // namespace
 
+class MediaRecorder::TrackEventListener final : public EventListener {
+public:
+    static PassRefPtrWillBeRawPtr<TrackEventListener> create(blink::WebMediaRecorderHandlerClient* client)
+    {
+        return adoptRefWillBeNoop(new TrackEventListener(client));
+    }
+
+    bool operator==(const EventListener& other) const override
+    {
+        return this == &other;
+    }
+
+private:
+    TrackEventListener(blink::WebMediaRecorderHandlerClient* client)
+        : EventListener(JSEventListenerType)
+        , m_client(client)
+    {
+    }
+
+    void handleEvent(ExecutionContext* executionContext, Event*) override
+    {
+        m_client->onError("MediaStream got a Track added/removed");
+    }
+
+    blink::WebMediaRecorderHandlerClient* const m_client;
+};
+
 MediaRecorder* MediaRecorder::create(ExecutionContext* context, MediaStream* stream, ExceptionState& exceptionState)
 {
     MediaRecorder* recorder = new MediaRecorder(context, stream, MediaRecorderOptions(), exceptionState);
@@ -76,6 +103,11 @@ MediaRecorder::MediaRecorder(ExecutionContext* context, MediaStream* stream, con
         exceptionState.throwDOMException(NotSupportedError, "Failed to initialize native MediaRecorder, the type provided " + m_mimeType + "is unsupported." );
         return;
     }
+
+    m_addOrRemoveTrackListener = TrackEventListener::create(this);
+    stream->addEventListener(EventTypeNames::addtrack, m_addOrRemoveTrackListener, false);
+    stream->addEventListener(EventTypeNames::removetrack, m_addOrRemoveTrackListener, false);
+
     m_stopped = false;
 }