mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/ws/event_dispatcher.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 "components/mus/ws/event_dispatcher.h"
 
 #include <set>
 
 #include "base/time/time.h"
 #include "cc/surfaces/surface_hittest.h"
@@ skipping 90 matching lines @@
     StopTrackingPointer(pointer_targets_.begin()->first);
 
   mouse_button_down_ = false;
 }
 
 void EventDispatcher::SetMousePointerScreenLocation(
     const gfx::Point& screen_location) {
   DCHECK(pointer_targets_.empty());
   mouse_pointer_last_location_ = screen_location;
   UpdateCursorProviderByLastKnownLocation();
+  delegate_->OnMouseCursorLocationChanged(screen_location);

[sky, 2016/04/18 15:09:11]

Why do you need to notify the delegate? Can't we query for the location from
EventDispatcher when needed?

 }
 
 bool EventDispatcher::SetCaptureWindow(ServerWindow* window,
                                        bool in_nonclient_area) {
   if (window == capture_window_)
     return true;
 
   // A window that is blocked by a modal window cannot gain capture.
   if (window && window->IsBlockedByModalWindow())
     return false;
@@ skipping 111 matching lines @@
   } else if (post_target) {
     delegate_->OnAccelerator(post_target->id(), event);
   }
 }
 
 void EventDispatcher::ProcessLocatedEvent(const ui::LocatedEvent& event) {
   DCHECK(event.IsPointerEvent() || event.IsMouseWheelEvent());
   const bool is_mouse_event =
       event.IsMousePointerEvent() || event.IsMouseWheelEvent();
 
-  if (is_mouse_event)
+  if (is_mouse_event && mouse_pointer_last_location_ != event.location()) {
+    delegate_->OnMouseCursorLocationChanged(event.location());
     mouse_pointer_last_location_ = event.location();
+  }
 
   // Release capture on pointer up. For mouse we only release if there are
   // no buttons down.
   const bool is_pointer_going_up =
       (event.type() == ui::ET_POINTER_UP ||
        event.type() == ui::ET_POINTER_CANCELLED) &&
       (!is_mouse_event || IsOnlyOneMouseButtonDown(event.flags()));
 
   // Update mouse down state upon events which change it.
   if (is_mouse_event) {
@@ skipping 192 matching lines @@
 
 void EventDispatcher::OnWindowDestroyed(ServerWindow* window) {
   CancelPointerEventsToTarget(window);
 
   if (mouse_cursor_source_window_ == window)
     mouse_cursor_source_window_ = nullptr;
 }
 
 }  // namespace ws
 }  // namespace mus