Check for valid webMediaPlayer() before using it.

Source/modules/webaudio/MediaElementAudioSourceNode.cpp

Index: Source/modules/webaudio/MediaElementAudioSourceNode.cpp
diff --git a/Source/modules/webaudio/MediaElementAudioSourceNode.cpp b/Source/modules/webaudio/MediaElementAudioSourceNode.cpp
index 92c558cb5a03d6ed632ea4fb075c9878357ae5d9..453bfa22a3be2e2f2b9226b3269520d81c00236d 100644
--- a/Source/modules/webaudio/MediaElementAudioSourceNode.cpp
+++ b/Source/modules/webaudio/MediaElementAudioSourceNode.cpp
@@ -129,6 +129,11 @@ void MediaElementAudioSourceNode::process(size_t numberOfFrames)
                 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.