cc: Force layer tree tests to go idle before exiting.

cc/thread_proxy.h

Index: cc/thread_proxy.h
diff --git a/cc/thread_proxy.h b/cc/thread_proxy.h
index da4f3868eddfb01ff385e71323e828bdcb731ae8..3d73f5261922f728d667f44ad86f9f4fb40fac92 100644
--- a/cc/thread_proxy.h
+++ b/cc/thread_proxy.h
@@ -53,6 +53,7 @@ public:
     virtual size_t maxPartialTextureUpdates() const OVERRIDE;
     virtual void acquireLayerTextures() OVERRIDE;
     virtual void forceSerializeOnSwapBuffers() OVERRIDE;
+    virtual bool commitPendingForTesting() OVERRIDE;
 
     // LayerTreeHostImplClient implementation
     virtual void didLoseOutputSurfaceOnImplThread() OVERRIDE;
@@ -106,6 +107,10 @@ private:
         void* pixels;
         gfx::Rect rect;
     };
+    struct CommitPendingRequest {
+        CompletionEvent completion;
+        bool commitPending;
+    };
     void forceBeginFrameOnImplThread(CompletionEvent*);
     void beginFrameCompleteOnImplThread(CompletionEvent*, ResourceUpdateQueue*);
     void beginFrameAbortedOnImplThread();
@@ -126,6 +131,7 @@ private:
     ScheduledActionDrawAndSwapResult scheduledActionDrawAndSwapInternal(bool forcedDraw);
     void forceSerializeOnSwapBuffersOnImplThread(CompletionEvent*);
     void setNeedsForcedCommitOnImplThread();
+    void commitPendingOnImplThreadForTesting(CommitPendingRequest* request);
 
     // Accessed on main thread only.
     bool m_animateRequested; // Set only when setNeedsAnimate is called.