Don't use PostTask queueing between compositor and main thread.

content/common/input/event_with_latency_info.h

Index: content/common/input/event_with_latency_info.h
diff --git a/content/common/input/event_with_latency_info.h b/content/common/input/event_with_latency_info.h
index cdfdb6ea1995309b9ee4140d9621a3772853712f..8c83e3e8ee96a0005f250150da2f0f42a6e64ca2 100644
--- a/content/common/input/event_with_latency_info.h
+++ b/content/common/input/event_with_latency_info.h
@@ -8,6 +8,7 @@
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "content/common/content_export.h"
+#include "content/common/input/scoped_web_input_event.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "ui/events/latency_info.h"
 
@@ -34,6 +35,27 @@ void CONTENT_EXPORT Coalesce(const blink::WebGestureEvent& event_to_coalesce,
 
 }  // namespace internal
 
+class ScopedWebInputEventWithLatencyInfo {
+ public:
+  ScopedWebInputEventWithLatencyInfo(const blink::WebInputEvent& e,
+                                     const ui::LatencyInfo& l);
+
+  ~ScopedWebInputEventWithLatencyInfo();
+
+  bool CanCoalesceWith(const ScopedWebInputEventWithLatencyInfo& other) const
+      WARN_UNUSED_RESULT;
+
+  const blink::WebInputEvent& event() const;
+  blink::WebInputEvent& event();
+  const ui::LatencyInfo latencyInfo() const { return latency_; }
+
+  void CoalesceWith(const ScopedWebInputEventWithLatencyInfo& other);
+
+ private:
+  ScopedWebInputEvent event_;
+  mutable ui::LatencyInfo latency_;

[tdresser, 2016/07/20 20:52:27]

I don't feel great about this being mutable. It's needed for coalescing, right?
Could we just make the event being coalesced non-const?

+};
+
 template <typename T>
 class EventWithLatencyInfo {
  public: