Fix NOTREACHED() in abortIfUpdating() when aborting 0-byte appendBuffer

third_party/WebKit/Source/modules/mediasource/SourceBuffer.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 464 matching lines @@
 {
     // Section 3.2 abort() method step 4 substeps.
     // http://w3c.github.io/media-source/#widl-SourceBuffer-abort-void
 
     if (!m_updating)
         return;
 
     DCHECK_EQ(m_pendingRemoveStart, -1);
 
     const char* traceEventName = 0;
-    if (!m_pendingAppendData.isEmpty()) {

[wolenetz, 2016/09/02 20:10:53]

It's entirely possible for pendingAppendData to be empty when aborting an
asynchronous 0-byte appendBuffer. This CL avoids the NOTREACHED() on debug
builds, and uses the correct traceEventName in all build types.

-        traceEventName = "SourceBuffer::appendBuffer";
-    } else if (m_stream) {
+    if (m_stream) {
         traceEventName = "SourceBuffer::appendStream";
     } else {
-        NOTREACHED();
+        traceEventName = "SourceBuffer::appendBuffer";
     }
 
     // 4.1. Abort the buffer append and stream append loop algorithms if they are running.
     m_appendBufferAsyncPartRunner->stop();
     m_pendingAppendData.clear();
     m_pendingAppendDataOffset = 0;
 
     m_appendStreamAsyncPartRunner->stop();
     clearAppendStreamState();
 
@@ skipping 759 matching lines @@
     visitor->trace(m_removeAsyncPartRunner);
     visitor->trace(m_appendStreamAsyncPartRunner);
     visitor->trace(m_stream);
     visitor->trace(m_audioTracks);
     visitor->trace(m_videoTracks);
     EventTargetWithInlineData::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink