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

cc/trees/proxy_main.cc

Index: cc/trees/proxy_main.cc
diff --git a/cc/trees/proxy_main.cc b/cc/trees/proxy_main.cc
index de79051d4b38e3395e219f1054e431150859bd37..ceb94415b7644988cb785549a71f82e21abb4b21 100644
--- a/cc/trees/proxy_main.cc
+++ b/cc/trees/proxy_main.cc
@@ -265,7 +265,17 @@ void ProxyMain::BeginMainFrame(
                               base::Unretained(proxy_impl_.get()), &completion,
                               layer_tree_host_, begin_main_frame_start_time,
                               hold_commit_for_activation));
-    completion.Wait();
+    // TODO(sunnyps): Remove this code once crbug.com/668892 is fixed.
+    // content/common/content_constants_internal.cc defines hung renderer delay
+    // as 30s so choose something less than that but still sufficiently long.
+    static constexpr base::TimeDelta kDumpDelay =
+        base::TimeDelta::FromSeconds(20);
+    if (!completion.TimedWait(kDumpDelay)) {
+      ImplThreadTaskRunner()->PostTask(
+          FROM_HERE, base::Bind(&ProxyImpl::DumpForBeginMainFrameHang,
+                                base::Unretained(proxy_impl_.get())));
+      completion.Wait();
+    }
   }
 
   current_pipeline_stage_ = NO_PIPELINE_STAGE;