Chrome requires WebTouchPoint to store WebFloatPoint, instead of WebPoint.

content/renderer/input/input_handler_proxy.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_proxy.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "content/common/input/web_input_event_traits.h"
 #include "content/renderer/input/input_handler_proxy_client.h"
 #include "third_party/WebKit/public/platform/Platform.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "ui/events/latency_info.h"
 #include "ui/gfx/frame_time.h"
+#include "ui/gfx/geometry/point_conversions.h"
 
 using blink::WebFloatPoint;
 using blink::WebFloatSize;
 using blink::WebGestureEvent;
 using blink::WebInputEvent;
 using blink::WebMouseEvent;
 using blink::WebMouseWheelEvent;
 using blink::WebPoint;
 using blink::WebTouchEvent;
 using blink::WebTouchPoint;
@@ skipping 198 matching lines @@
       return DID_HANDLE;
     else if (!fling_may_be_active_on_main_thread_)
       return DROP_EVENT;
   } else if (event.type == WebInputEvent::TouchStart) {
     const WebTouchEvent& touch_event =
         *static_cast<const WebTouchEvent*>(&event);
     for (size_t i = 0; i < touch_event.touchesLength; ++i) {
       if (touch_event.touches[i].state != WebTouchPoint::StatePressed)
         continue;
       if (input_handler_->HaveTouchEventHandlersAt(
-              blink::WebPoint(touch_event.touches[i].position.x,
-                              touch_event.touches[i].position.y))) {
+              gfx::ToFlooredPoint(touch_event.touches[i].position))) {

[jdduke (slow), 2014/03/20 12:11:34]

Hmm, this may be a small change in behavior.  Previously, the coords were
truncated, but now they're being floored, no?  Can we just use gfx::Point()
constructor here, and eventually we should update the method to take a
gfx::PointF.

[tdresser, 2014/03/20 14:09:14]

Done. 

I'm not convinced it really makes sense to make HaveTouchEventHandlersAt take a
gfx::PointF. Patch #4 did this, but I couldn't see much benefit. Why do you
think it would be preferable?

         return DID_NOT_HANDLE;
       }
     }
     return DROP_EVENT;
   } else if (WebInputEvent::isKeyboardEventType(event.type)) {
     CancelCurrentFling(true);
   } else if (event.type == WebInputEvent::MouseMove) {
     const WebMouseEvent& mouse_event =
         *static_cast<const WebMouseEvent*>(&event);
     // TODO(tony): Ignore when mouse buttons are down?
@@ skipping 243 matching lines @@
   TRACE_EVENT2("input",
                "InputHandlerProxy::notifyCurrentFlingVelocity",
                "vx",
                velocity.width,
                "vy",
                velocity.height);
   input_handler_->NotifyCurrentFlingVelocity(ToClientScrollIncrement(velocity));
 }
 
 }  // namespace content