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

services/ui/ws/display_manager.cc

 // Copyright 2016 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 "services/ui/ws/display_manager.h"
 
 #include <vector>
 
 #include "base/memory/ptr_util.h"
 #include "base/stl_util.h"
@@ skipping 286 matching lines @@
   for (Display* display : displays_) {
     display->platform_display()->GetFrameGenerator()->SetHighContrastMode(
         enabled);
   }
 }
 
 void DisplayManager::OnActiveUserIdChanged(const UserId& previously_active_id,
                                            const UserId& active_id) {
   WindowManagerState* previous_window_manager_state =
       window_server_->GetWindowManagerStateForUser(previously_active_id);
-  gfx::Point mouse_location_on_screen;
+  gfx::Point mouse_location_on_display;
+  int64_t mouse_display_id = 0;
   if (previous_window_manager_state) {
-    mouse_location_on_screen = previous_window_manager_state->event_dispatcher()
-                                   ->mouse_pointer_last_location();
+    mouse_location_on_display =
+        previous_window_manager_state->event_dispatcher()
+            ->mouse_pointer_last_location();
+    mouse_display_id = previous_window_manager_state->event_dispatcher()
+                           ->mouse_pointer_display_id();
     previous_window_manager_state->Deactivate();
   }
 
   WindowManagerState* current_window_manager_state =
       window_server_->GetWindowManagerStateForUser(active_id);
   if (current_window_manager_state)
-    current_window_manager_state->Activate(mouse_location_on_screen);
+    current_window_manager_state->Activate(mouse_location_on_display,
+                                           mouse_display_id);
 }
 
 void DisplayManager::CreateDisplay(const display::Display& display,
                                    const display::ViewportMetrics& metrics) {
   ws::Display* ws_display = new ws::Display(window_server_);
   ws_display->SetDisplay(display);
   ws_display->Init(metrics, nullptr);
 }
 
 void DisplayManager::OnDisplayAdded(const display::Display& display,
@@ skipping 39 matching lines @@
   DVLOG(3) << "OnPrimaryDisplayChanged: " << primary_display_id;
   // TODO(kylechar): Send IPCs to WM clients first.
 
   // Send IPCs to any DisplayManagerObservers.
   for (const auto& pair : user_display_managers_)
     pair.second->OnPrimaryDisplayChanged(primary_display_id);
 }
 
 }  // namespace ws
 }  // namespace ui