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

content/common/input/input_event_ack.h

Index: content/common/input/input_event_ack.h
diff --git a/content/common/input/input_event_ack.h b/content/common/input/input_event_ack.h
index 66b003d4a5f48fc6b52df83d7e1c27561b617afb..95401839eacdeeded351db5374813d0dc1d7ded3 100644
--- a/content/common/input/input_event_ack.h
+++ b/content/common/input/input_event_ack.h
@@ -10,6 +10,7 @@
 #include <memory>
 
 #include "content/common/content_export.h"
+#include "content/common/input/input_event_ack_source.h"
 #include "content/common/input/input_event_ack_state.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "ui/events/blink/did_overscroll_params.h"
@@ -19,22 +20,28 @@ namespace content {
 
 // InputEventAck.
 struct CONTENT_EXPORT InputEventAck {
-  InputEventAck(blink::WebInputEvent::Type type,
+  InputEventAck(InputEventAckSource source,
+                blink::WebInputEvent::Type type,
                 InputEventAckState state,
                 const ui::LatencyInfo& latency,
                 std::unique_ptr<ui::DidOverscrollParams> overscroll,
                 uint32_t unique_touch_event_id);
-  InputEventAck(blink::WebInputEvent::Type type,
+  InputEventAck(InputEventAckSource source,
+                blink::WebInputEvent::Type type,
                 InputEventAckState state,
                 const ui::LatencyInfo& latency,
                 uint32_t unique_touch_event_id);
-  InputEventAck(blink::WebInputEvent::Type type,
+  InputEventAck(InputEventAckSource source,
+                blink::WebInputEvent::Type type,
                 InputEventAckState state,
                 uint32_t unique_touch_event_id);
-  InputEventAck(blink::WebInputEvent::Type type, InputEventAckState state);
+  InputEventAck(InputEventAckSource source,
+                blink::WebInputEvent::Type type,
+                InputEventAckState state);
   InputEventAck();
   ~InputEventAck();
 
+  InputEventAckSource source;
   blink::WebInputEvent::Type type;
   InputEventAckState state;
   ui::LatencyInfo latency;