Check for valid webMediaPlayer() before using it.

Source/modules/webaudio/MediaElementAudioSourceNode.cpp

 /*
  * Copyright (C) 2011, 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:
  * 1.  Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 111 matching lines @@
             // Grab data from the provider so that the element continues to make progress, even if
             // we're going to output silence anyway.
             if (m_multiChannelResampler.get()) {
                 ASSERT(m_sourceSampleRate != sampleRate());
                 m_multiChannelResampler->process(provider, outputBus, numberOfFrames);
             } else {
                 // Bypass the resampler completely if the source is at the context's sample-rate.
                 ASSERT(m_sourceSampleRate == sampleRate());
                 provider->provideInput(outputBus, numberOfFrames);
             }
+            // Output silence if we don't have access to the element.
+            if (!((mediaElement()->webMediaPlayer() && mediaElement()->webMediaPlayer()->didPassCORSAccessCheck())
+                || context()->securityOrigin()->canRequest(mediaElement()->currentSrc()))) {
+                outputBus->zero();
+            }
         } else {
             // Either this port doesn't yet support HTMLMediaElement audio stream access,
             // or the stream is not yet available.
             outputBus->zero();
         }
     } else {
         // We failed to acquire the lock.
         outputBus->zero();
     }
 }
@@ skipping 11 matching lines @@
 void MediaElementAudioSourceNode::trace(Visitor* visitor)
 {
     visitor->trace(m_mediaElement);
     AudioSourceNode::trace(visitor);
     AudioSourceProviderClient::trace(visitor);
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)