Don't run removeFinishedSourceNodes with the context lock.

third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp

Index: third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
index bf0da224144f6cac26f789b0ad6028ca6bc19895..87f23d7c93629bcc27c82b59b6971a040bd57d8d 100644
--- a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -36,8 +36,10 @@
 #include "modules/webaudio/OfflineAudioCompletionEvent.h"
 #include "modules/webaudio/OfflineAudioDestinationNode.h"
 
+#include "platform/CrossThreadFunctional.h"
 #include "platform/Histogram.h"
 #include "platform/audio/AudioUtilities.h"
+#include "public/platform/Platform.h"
 
 namespace blink {
 
@@ -374,12 +376,21 @@ void OfflineAudioContext::handlePostOfflineRenderTasks() {
 
   // OfflineGraphAutoLocker here locks the audio graph for the same reason
   // above in |handlePreOfflineRenderTasks|.
-  OfflineGraphAutoLocker locker(this);
-
-  deferredTaskHandler().breakConnections();
-  releaseFinishedSourceNodes();
-  deferredTaskHandler().handleDeferredTasks();
-  deferredTaskHandler().requestToDeleteHandlersOnMainThread();
+  bool didRemove = false;
+  {
+    OfflineGraphAutoLocker locker(this);
+
+    deferredTaskHandler().breakConnections();
+    didRemove = releaseFinishedSourceNodes();
+    deferredTaskHandler().handleDeferredTasks();
+    deferredTaskHandler().requestToDeleteHandlersOnMainThread();
+  }
+  if (didRemove) {
+    Platform::current()->mainThread()->getWebTaskRunner()->postTask(
+        BLINK_FROM_HERE,
+        crossThreadBind(&BaseAudioContext::removeFinishedSourceNodes,
+                        wrapCrossThreadPersistent(this)));
+  }
 }
 
 OfflineAudioDestinationHandler& OfflineAudioContext::destinationHandler() {