Don't restart the hang renderer timeout on messages ack'd from the compositor thread.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 14a3e97ea2d7698f053d971bfdde86b86d814da8..2214f82fa25c0a4c16489027b71f9b6c4468f4c7 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -2997,7 +2997,8 @@ void RenderViewImpl::OnDiscardInputEvent(
   }
 
   std::unique_ptr<InputEventAck> ack(
-      new InputEventAck(input_event->type, INPUT_EVENT_ACK_STATE_NOT_CONSUMED));
+      new InputEventAck(InputEventAckSource::MAIN_THREAD, input_event->type,
+                        INPUT_EVENT_ACK_STATE_NOT_CONSUMED));
   OnInputEventAck(std::move(ack));
 }