Implement Wheel Gesture Scrolling on OSX.

content/renderer/input/render_widget_input_handler.cc

 // Copyright 2015 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/render_widget_input_handler.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
 
@@ skipping 349 matching lines @@
           delegate_->HasTouchEventHandlersAt(
               gfx::ToFlooredPoint(touch_event.touches[i].position))) {
         ack_result = INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
         break;
       }
     }
   }
 
   // Send mouse wheel events and their disposition to the compositor thread, so
   // that they can be used to produce the elastic overscroll effect on Mac.
   if (input_event.type == WebInputEvent::MouseWheel) {

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

We should make sure that removing all the wheel specific code is part of the
plan here.

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

Acknowledged.

     const WebMouseWheelEvent& wheel_event =
         static_cast<const WebMouseWheelEvent&>(input_event);
     if (wheel_event.canScroll) {
       delegate_->ObserveWheelEventAndResult(
           wheel_event,
           event_overscroll ? event_overscroll->latest_overscroll_delta
                            : gfx::Vector2dF(),
           processed != WebInputEventResult::NotHandled);
     }
+  } else if (input_event.type == WebInputEvent::GestureScrollBegin ||
+             input_event.type == WebInputEvent::GestureScrollEnd ||
+             input_event.type == WebInputEvent::GestureScrollUpdate) {
+    const WebGestureEvent& gesture_event =
+        static_cast<const WebGestureEvent&>(input_event);
+    if (gesture_event.sourceDevice == blink::WebGestureDeviceTouchpad) {
+      delegate_->ObserveGestureEventAndResult(
+          gesture_event,
+          event_overscroll ? event_overscroll->latest_overscroll_delta
+                           : gfx::Vector2dF(),
+          processed != WebInputEventResult::NotHandled);
+    }
   }
 
   bool frame_pending =
       widget_->compositor() && widget_->compositor()->BeginMainFrameRequested();
 
   // If we don't have a fast and accurate Now(), we assume the input handlers
   // are heavy and rate limit them.
   bool rate_limiting_wanted = input_event.type == WebInputEvent::MouseMove ||
                               input_event.type == WebInputEvent::MouseWheel;
   if (rate_limiting_wanted && !start_time.is_null()) {
@@ skipping 137 matching lines @@
   if (pending_input_event_ack_) {
     TRACE_EVENT_ASYNC_END0("input",
                            "RenderWidgetInputHandler::ThrottledInputEventAck",
                            pending_input_event_ack_.get());
     delegate_->OnInputEventAck(std::move(pending_input_event_ack_));
   }
   total_input_handling_time_this_frame_ = base::TimeDelta();
 }
 
 }  // namespace content