Keep root_location to be in pixels and display coordinates in WS.

services/ui/ws/event_dispatcher.h

Index: services/ui/ws/event_dispatcher.h
diff --git a/services/ui/ws/event_dispatcher.h b/services/ui/ws/event_dispatcher.h
index 8b084d7994f697a555d078ac1023b4dc5336f825..7890d14985a198c8eb178685a7660660ec3b6e87 100644
--- a/services/ui/ws/event_dispatcher.h
+++ b/services/ui/ws/event_dispatcher.h
@@ -59,10 +59,12 @@ class EventDispatcher : public ServerWindowObserver, public DragCursorUpdater {
   // any events to the delegate.
   void Reset();
 
-  void SetMousePointerScreenLocation(const gfx::Point& screen_location);
+  void SetMousePointerDisplayLocationAndId(const gfx::Point& display_location,

[sky, 2017/05/17 16:53:41]

optional: the new name is rather verbose. Leave the old name, and add
display_id.

[riajiang, 2017/05/19 20:45:05]

Done.

+                                           const int64_t display_id);
   const gfx::Point& mouse_pointer_last_location() const {
     return mouse_pointer_last_location_;
   }
+  int64_t mouse_pointer_display_id() const { return mouse_pointer_display_id_; }
 
   // Returns the cursor for the current target, or POINTER if the mouse is not
   // over a valid target.
@@ -142,7 +144,9 @@ class EventDispatcher : public ServerWindowObserver, public DragCursorUpdater {
   // ANY and there is a matching accelerator with PRE_TARGET found, than only
   // OnAccelerator() is called. The expectation is after the PRE_TARGET has been
   // handled this is again called with an AcceleratorMatchPhase of POST_ONLY.
-  void ProcessEvent(const ui::Event& event, AcceleratorMatchPhase match_phase);
+  void ProcessEvent(const ui::Event& event,
+                    const int64_t display_id,
+                    AcceleratorMatchPhase match_phase);
 
  private:
   friend class test::EventDispatcherTestApi;
@@ -186,7 +190,8 @@ class EventDispatcher : public ServerWindowObserver, public DragCursorUpdater {
   //   when no buttons on the mouse are down.
   // This also generates exit events as appropriate. For example, if the mouse
   // moves between one window to another an exit is generated on the first.
-  void ProcessPointerEvent(const ui::PointerEvent& event);
+  void ProcessPointerEvent(const ui::PointerEvent& event,
+                           const int64_t display_id);
 
   // Adds |pointer_target| to |pointer_targets_|.
   void StartTrackingPointer(int32_t pointer_id,
@@ -234,7 +239,8 @@ class EventDispatcher : public ServerWindowObserver, public DragCursorUpdater {
   Accelerator* FindAccelerator(const ui::KeyEvent& event,
                                const ui::mojom::AcceleratorPhase phase);
 
-  DeepestWindow FindDeepestVisibleWindowForEvents(const gfx::Point& location);
+  DeepestWindow FindDeepestVisibleWindowForEvents(gfx::Point* location,
+                                                  int64_t* display_id);
 
   // Clears the implicit captures in |pointer_targets_|, with the exception of
   // |window|. |window| may be null. |client_id| is the target client of
@@ -265,9 +271,15 @@ class EventDispatcher : public ServerWindowObserver, public DragCursorUpdater {
   ServerWindow* mouse_cursor_source_window_;
   bool mouse_cursor_in_non_client_area_;
 
-  // The on screen location of the mouse pointer. This can be outside the
-  // bounds of |mouse_cursor_source_window_|, which can capture the cursor.
+  // The location of the mouse pointer in display coordinates. This can be
+  // outside the bounds of |mouse_cursor_source_window_|, which can capture the
+  // cursor.
   gfx::Point mouse_pointer_last_location_;
+  // Id of the display |mouse_pointer_last_location_| is on.
+  int64_t mouse_pointer_display_id_ = 0;
+
+  // Id of the display the most recent event is on.

[sky, 2017/05/17 16:53:41]

Under what circumstances is mouse_pointer_display_id and event_dispaly_id_
different?

[riajiang, 2017/05/19 20:45:05]

We don't update mouse specific info (mouse_pointer_last_location_ and
mouse_pointer_display_id_) if the event coming in is not a mouse event, but
event_display_id_ would be changed in that case. 

+  int64_t event_display_id_ = 0;
 
   std::map<uint32_t, std::unique_ptr<Accelerator>> accelerators_;