Refactor compositor event handling path to be callback-based

content/renderer/input/input_handler_manager.cc

Index: content/renderer/input/input_handler_manager.cc
diff --git a/content/renderer/input/input_handler_manager.cc b/content/renderer/input/input_handler_manager.cc
index 7fd9096da2b44bdaea666f727f5c9ae14b29611d..69354f6ac6b3a56a6b1c52f27332859299ef5c9a 100644
--- a/content/renderer/input/input_handler_manager.cc
+++ b/content/renderer/input/input_handler_manager.cc
@@ -13,7 +13,6 @@
 #include "base/trace_event/trace_event.h"
 #include "cc/input/input_handler.h"
 #include "content/renderer/input/input_event_filter.h"
-#include "content/renderer/input/input_handler_manager_client.h"
 #include "content/renderer/input/input_handler_wrapper.h"
 #include "third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h"
 #include "ui/events/blink/did_overscroll_params.h"
@@ -193,10 +192,11 @@ void InputHandlerManager::NotifyInputEventHandledOnMainThread(
   client_->NotifyInputEventHandled(routing_id, type, ack_result);
 }
 
-InputEventAckState InputHandlerManager::HandleInputEvent(
+void InputHandlerManager::HandleInputEvent(
     int routing_id,
-    const WebInputEvent* input_event,
-    ui::LatencyInfo* latency_info) {
+    ui::ScopedWebInputEvent input_event,
+    const ui::LatencyInfo& latency_info,
+    const InputEventAckStateCallback& callback) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   TRACE_EVENT1("input,benchmark,rail", "InputHandlerManager::HandleInputEvent",
                  "type", ui::WebInputEventTraits::GetName(input_event->type));
@@ -206,14 +206,28 @@ InputEventAckState InputHandlerManager::HandleInputEvent(
     TRACE_EVENT1("input,rail", "InputHandlerManager::HandleInputEvent",
                  "result", "NoInputHandlerFound");
     // Oops, we no longer have an interested input handler..
-    return INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
+    callback.Run(INPUT_EVENT_ACK_STATE_NOT_CONSUMED, std::move(input_event),
+                 latency_info, nullptr);
+    return;
   }
 
   TRACE_EVENT1("input,rail", "InputHandlerManager::HandleInputEvent",
                "result", "EventSentToInputHandlerProxy");
   InputHandlerProxy* proxy = it->second->input_handler_proxy();
-  InputEventAckState input_event_ack_state = InputEventDispositionToAck(
-      proxy->HandleInputEventWithLatencyInfo(*input_event, latency_info));
+  proxy->HandleInputEventWithLatencyInfo(
+      std::move(input_event), latency_info,
+      base::Bind(&InputHandlerManager::DidHandleInputEvent,
+                 base::Unretained(this), callback));
+}
+
+void InputHandlerManager::DidHandleInputEvent(
+    const InputEventAckStateCallback& callback,
+    EventDisposition event_disposition,
+    ui::ScopedWebInputEvent input_event,
+    const ui::LatencyInfo& latency_info,
+    std::unique_ptr<ui::DidOverscrollParams> overscroll_params) {
+  InputEventAckState input_event_ack_state =
+      InputEventDispositionToAck(event_disposition);
   switch (input_event_ack_state) {
     case INPUT_EVENT_ACK_STATE_CONSUMED:
       renderer_scheduler_->DidHandleInputEventOnCompositorThread(
@@ -228,12 +242,14 @@ InputEventAckState InputHandlerManager::HandleInputEvent(
     default:
       break;
   }
-  return input_event_ack_state;
+  callback.Run(input_event_ack_state, std::move(input_event), latency_info,
+               std::move(overscroll_params));
 }
 
 void InputHandlerManager::DidOverscroll(int routing_id,
-                                        const ui::DidOverscrollParams& params) {
-  client_->DidOverscroll(routing_id, params);
+                                        const ui::DidOverscrollParams& params,
+                                        bool bundle_ack_with_triggering_event) {
+  client_->DidOverscroll(routing_id, params, bundle_ack_with_triggering_event);
 }
 
 void InputHandlerManager::DidStartFlinging(int routing_id) {