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

content/renderer/input/input_event_filter.cc

Index: content/renderer/input/input_event_filter.cc
diff --git a/content/renderer/input/input_event_filter.cc b/content/renderer/input/input_event_filter.cc
index 56799b1128b224d40efe5c5edff70d23b09efa44..cf24f928250567a9d55f71539dc06388c8ae8517 100644
--- a/content/renderer/input/input_event_filter.cc
+++ b/content/renderer/input/input_event_filter.cc
@@ -264,7 +264,8 @@ void InputEventFilter::DidForwardToHandlerAndOverscroll(
   if (!send_ack)
     return;
 
-  InputEventAck ack(type, ack_state, latency_info, std::move(overscroll_params),
+  InputEventAck ack(InputEventAckSource::COMPOSITOR_THREAD, type, ack_state,
+                    latency_info, std::move(overscroll_params),
                     unique_touch_event_id);
   SendMessage(std::unique_ptr<IPC::Message>(
       new InputHostMsg_HandleInputEvent_ACK(routing_id, ack)));
@@ -302,7 +303,9 @@ void InputEventFilter::SendInputEventAck(int routing_id,
                                          blink::WebInputEvent::Type type,
                                          InputEventAckState ack_result,
                                          uint32_t touch_event_id) {
-  InputEventAck ack(type, ack_result, touch_event_id);
+  DCHECK(main_task_runner_->BelongsToCurrentThread());
+  InputEventAck ack(InputEventAckSource::MAIN_THREAD, type, ack_result,
+                    touch_event_id);
   SendMessage(std::unique_ptr<IPC::Message>(
       new InputHostMsg_HandleInputEvent_ACK(routing_id, ack)));
 }