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

services/ui/ws/window_manager_state.h

Index: services/ui/ws/window_manager_state.h
diff --git a/services/ui/ws/window_manager_state.h b/services/ui/ws/window_manager_state.h
index ce897244a81ee49e82e48e4f17faf0a33184868e..8e98b95e26b8174b7ca61fa88f3d5fde6823f740 100644
--- a/services/ui/ws/window_manager_state.h
+++ b/services/ui/ws/window_manager_state.h
@@ -96,7 +96,8 @@ class WindowManagerState : public EventDispatcherDelegate,
   // Returns true if this is the WindowManager of the active user.
   bool IsActive() const;
 
-  void Activate(const gfx::Point& mouse_location_on_screen);
+  void Activate(const gfx::Point& mouse_location_on_display,
+                const int64_t display_id);
   void Deactivate();
 
   // Processes an event from PlatformDisplay.
@@ -240,6 +241,9 @@ class WindowManagerState : public EventDispatcherDelegate,
                                  const Event& event,
                                  EventDispatchPhase phase);
 
+  // Helper function to update |point| to be in screen coordinates.
+  bool ConvertPointToScreen(gfx::Point* point, const int64_t display_id);
+
   // EventDispatcherDelegate:
   void OnAccelerator(uint32_t accelerator_id,
                      const Event& event,
@@ -251,14 +255,16 @@ class WindowManagerState : public EventDispatcherDelegate,
   void UpdateNativeCursorFromDispatcher() override;
   void OnCaptureChanged(ServerWindow* new_capture,
                         ServerWindow* old_capture) override;
-  void OnMouseCursorLocationChanged(const gfx::Point& point) override;
+  void OnMouseCursorLocationChanged(const gfx::Point& point,
+                                    const int64_t display_id) override;
   void DispatchInputEventToWindow(ServerWindow* target,
                                   ClientSpecificId client_id,
                                   const Event& event,
                                   Accelerator* accelerator) override;
   ClientSpecificId GetEventTargetClientId(const ServerWindow* window,
                                           bool in_nonclient_area) override;
-  ServerWindow* GetRootWindowContaining(gfx::Point* location) override;
+  ServerWindow* GetRootWindowContaining(gfx::Point* location_in_display,
+                                        int64_t* display_id) override;
   void OnEventTargetNotFound(const Event& event) override;
 
   // ServerWindowObserver: