exo: Fix multi-display hardware cursor

ash/wm/ash_native_cursor_manager.cc

 // Copyright (c) 2012 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 "ash/wm/ash_native_cursor_manager.h"
 
 #include "ash/display/cursor_window_controller.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/shell.h"
 #include "base/logging.h"
@@ skipping 42 matching lines @@
   // Mirror window never process events.
 }
 
 }  // namespace
 
 AshNativeCursorManager::AshNativeCursorManager()
     : native_cursor_enabled_(true), image_cursors_(new ui::ImageCursors) {}
 
 AshNativeCursorManager::~AshNativeCursorManager() {}
 
+void AshNativeCursorManager::AddObserver(Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void AshNativeCursorManager::RemoveObserver(Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 void AshNativeCursorManager::SetNativeCursorEnabled(bool enabled) {
   native_cursor_enabled_ = enabled;
 
   ::wm::CursorManager* cursor_manager = Shell::GetInstance()->cursor_manager();
   SetCursor(cursor_manager->GetCursor(), cursor_manager);
 }
 
 void AshNativeCursorManager::SetDisplay(
     const display::Display& display,
     ::wm::NativeCursorManagerDelegate* delegate) {
   DCHECK(display.is_valid());
+
+  for (Observer& observer : observers_)
+    observer.OnCursorDisplayChanging(display);
+
   // Use the platform's device scale factor instead of the display's, which
   // might have been adjusted for the UI scale.
   const float original_scale = Shell::GetInstance()
                                    ->display_manager()
                                    ->GetDisplayInfo(display.id())
                                    .device_scale_factor();
   // And use the nearest resource scale factor.
   const float cursor_scale =
       ui::GetScaleForScaleFactor(ui::GetSupportedScaleFactor(original_scale));
 
@@ skipping 72 matching lines @@
         disabled_cursor_location_);
   } else {
     disabled_cursor_location_ = aura::Env::GetInstance()->last_mouse_location();
   }
 
   SetVisibility(delegate->IsCursorVisible(), delegate);
   NotifyMouseEventsEnableStateChange(enabled);
 }
 
 }  // namespace ash