Prevent audio thread access to finished, non-active AudioNodes.

third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.h

Index: third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.h
diff --git a/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.h b/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.h
index a0c44233399c801f7aca3c235faedc4a1f77c1a6..c20bc028f496cc6d47ab09d41cee1704eee4f42b 100644
--- a/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.h
+++ b/third_party/WebKit/Source/modules/webaudio/AbstractAudioContext.h
@@ -320,7 +320,7 @@ private:
     // are performed by it. When the audio thread marks a source node as finished,
     // the nodes are added to |m_finishedSourceNodes| and scheduled for removal
     // from |m_activeSourceNodes| by the main thread.
-    Vector<UntracedMember<AudioNode>> m_finishedSourceNodes;
+    HashSet<UntracedMember<AudioNode>> m_finishedSourceNodes;
 
     // FIXME(dominicc): Move these to AudioContext because only
     // it creates these Promises.