Refactor compositor event handling path to be callback-based

content/renderer/mus/compositor_mus_connection.h

Index: content/renderer/mus/compositor_mus_connection.h
diff --git a/content/renderer/mus/compositor_mus_connection.h b/content/renderer/mus/compositor_mus_connection.h
index b344e2aac6b5ca33c4c36111d925fe40036bbae3..54b971bae80ae41a3c2fa49112d2b727b6344771 100644
--- a/content/renderer/mus/compositor_mus_connection.h
+++ b/content/renderer/mus/compositor_mus_connection.h
@@ -9,11 +9,13 @@
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "content/common/content_export.h"
+#include "content/common/input/input_event_ack_state.h"
 #include "services/ui/public/cpp/input_event_handler.h"
 #include "services/ui/public/cpp/window.h"
 #include "services/ui/public/cpp/window_tree_client.h"
 #include "services/ui/public/cpp/window_tree_client_delegate.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
+#include "ui/events/blink/scoped_web_input_event.h"
 
 namespace ui {
 struct DidOverscrollParams;
@@ -62,7 +64,7 @@ class CONTENT_EXPORT CompositorMusConnection
   void OnConnectionLostOnMainThread();
 
   void OnWindowInputEventOnMainThread(
-      std::unique_ptr<blink::WebInputEvent> web_event,
+      ui::ScopedWebInputEvent web_event,
       const base::Callback<void(ui::mojom::EventResult)>& ack);
 
   void OnWindowInputEventAckOnMainThread(
@@ -81,6 +83,13 @@ class CONTENT_EXPORT CompositorMusConnection
       const ui::Event& event,
       std::unique_ptr<base::Callback<void(ui::mojom::EventResult)>>*
           ack_callback) override;
+  void DidHandleWindowInputEventAndOverscroll(
+      std::unique_ptr<base::Callback<void(ui::mojom::EventResult)>>
+          ack_callback,
+      InputEventAckState ack_state,
+      ui::ScopedWebInputEvent web_event,
+      const ui::LatencyInfo& latency_info,
+      std::unique_ptr<ui::DidOverscrollParams>);
 
   const int routing_id_;
   ui::Window* root_;