Implement Wheel Gesture Scrolling on OSX.

content/renderer/input/input_handler_manager.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/input/input_handler_manager.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 126 matching lines @@
   auto it = input_handlers_.find(routing_id);
   if (it == input_handlers_.end())
     return;
 
   InputHandlerProxy* proxy = it->second->input_handler_proxy();
   DCHECK(proxy->scroll_elasticity_controller());
   proxy->scroll_elasticity_controller()->ObserveWheelEventAndResult(
       wheel_event, scroll_result);
 }
 
+void InputHandlerManager::ObserveGestureEventAndResultOnMainThread(
+    int routing_id,
+    const blink::WebGestureEvent& gesture_event,
+    const cc::InputHandlerScrollResult& scroll_result) {

[tdresser, 2016/03/02 18:26:53]

Should we check that we're on the correct thread here?

[dtapuska, 2016/03/07 18:03:59]

I've added a check in the OnCompositorThread since that is an affirmative check;
adding it here OnMainThread might not be wise since task_runner_ could in-fact
be the same thread as the main thread.

+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &InputHandlerManager::ObserveGestureEventAndResultOnCompositorThread,
+          base::Unretained(this), routing_id, gesture_event, scroll_result));
+}
+
+void InputHandlerManager::ObserveGestureEventAndResultOnCompositorThread(
+    int routing_id,
+    const blink::WebGestureEvent& gesture_event,
+    const cc::InputHandlerScrollResult& scroll_result) {
+  auto it = input_handlers_.find(routing_id);
+  if (it == input_handlers_.end())
+    return;
+
+  InputHandlerProxy* proxy = it->second->input_handler_proxy();
+  DCHECK(proxy->scroll_elasticity_controller());
+  proxy->scroll_elasticity_controller()->ObserveGestureEventAndResult(
+      gesture_event, scroll_result);
+}
+
 void InputHandlerManager::NonBlockingInputEventHandledOnMainThread(
     int routing_id,
     blink::WebInputEvent::Type type) {
   task_runner_->PostTask(
       FROM_HERE,
       base::Bind(
           &InputHandlerManager::NonBlockingInputEventHandledOnCompositorThread,
           base::Unretained(this), routing_id, type));
 }
 
@@ skipping 53 matching lines @@
 
 void InputHandlerManager::DidStopFlinging(int routing_id) {
   client_->DidStopFlinging(routing_id);
 }
 
 void InputHandlerManager::DidAnimateForInput() {
   renderer_scheduler_->DidAnimateForInputOnCompositorThread();
 }
 
 }  // namespace content