cc: Dump scheduler and tile manager state when commit is blocked.

cc/trees/proxy_impl.h

Index: cc/trees/proxy_impl.h
diff --git a/cc/trees/proxy_impl.h b/cc/trees/proxy_impl.h
index a0482ea2ff89449a7c97249c20c24457d919c318..68edc33451565e28889a564fc6461dddfd24a2d0 100644
--- a/cc/trees/proxy_impl.h
+++ b/cc/trees/proxy_impl.h
@@ -56,6 +56,8 @@ class CC_EXPORT ProxyImpl : public NON_EXPORTED_BASE(LayerTreeHostImplClient),
   void MainFrameWillHappenOnImplForTesting(CompletionEvent* completion,
                                            bool* main_frame_will_happen);
 
+  NOINLINE void DumpForBeginMainFrameHang();
+
  private:
   // The members of this struct should be accessed on the impl thread only when
   // the main thread is blocked for a commit.