Rename ContextDestructionObserver to ContextLifecycleObserver

Source/modules/mediastream/UserMediaRequest.h

Index: Source/modules/mediastream/UserMediaRequest.h
diff --git a/Source/modules/mediastream/UserMediaRequest.h b/Source/modules/mediastream/UserMediaRequest.h
index c539b1bb19503c57570fa21bdb72481f3109c000..2a485c6593c9973c6c4cc23a863c33b4928b9e47 100644
--- a/Source/modules/mediastream/UserMediaRequest.h
+++ b/Source/modules/mediastream/UserMediaRequest.h
@@ -50,7 +50,7 @@ class MediaConstraintsImpl;
 class MediaStreamDescriptor;
 class UserMediaController;
 
-class UserMediaRequest : public MediaStreamSourcesQueryClient, public ContextDestructionObserver {
+class UserMediaRequest : public MediaStreamSourcesQueryClient, public ContextLifecycleObserver {
 public:
     static PassRefPtr<UserMediaRequest> create(ScriptExecutionContext*, UserMediaController*, const Dictionary& options, PassRefPtr<NavigatorUserMediaSuccessCallback>, PassRefPtr<NavigatorUserMediaErrorCallback>, ExceptionCode&);
     ~UserMediaRequest();
@@ -73,7 +73,7 @@ public:
     virtual bool video() const;
     virtual void didCompleteQuery(const MediaStreamSourceVector& audioSources, const MediaStreamSourceVector& videoSources);
 
-    // ContextDestructionObserver
+    // ContextLifecycleObserver
     virtual void contextDestroyed();
 
 private: