Validate execution context before printing CORS message

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 91d945b1f63c1a1f81ccbe8719fdc164eb4349ff..3974efb758ae1f6e5bea9f66bbf568b4bd75bfc1 100644
--- a/Source/modules/webaudio/MediaElementAudioSourceNode.cpp
+++ b/Source/modules/webaudio/MediaElementAudioSourceNode.cpp
@@ -141,9 +141,11 @@ bool MediaElementAudioSourceHandler::passesCurrentSrcCORSAccessCheck(const KURL&
 
 void MediaElementAudioSourceHandler::printCORSMessage(const String& message)
 {
-    context()->executionContext()->addConsoleMessage(
-        ConsoleMessage::create(SecurityMessageSource, InfoMessageLevel,
-            "MediaElementAudioSource outputs zeroes due to CORS access restrictions for " + message));
+    if (context()->executionContext()) {

[hongchan, 2015/06/16 16:12:10]

What happens if executionContext() does not exist? Is it even possible? (Perhaps
the context from a closed tab?)

+        context()->executionContext()->addConsoleMessage(
+            ConsoleMessage::create(SecurityMessageSource, InfoMessageLevel,
+                "MediaElementAudioSource outputs zeroes due to CORS access restrictions for " + message));
+    }
 }
 
 void MediaElementAudioSourceHandler::process(size_t numberOfFrames)