mash: Migrate ash::DragImageView to wm common types

ash/drag_drop/drag_drop_controller.h

Index: ash/drag_drop/drag_drop_controller.h
diff --git a/ash/drag_drop/drag_drop_controller.h b/ash/drag_drop/drag_drop_controller.h
index dbe26583ff3c53a2f5098ef8146391c5aaf8223c..7b5d42cabe463e2355c4770a22b7fa2452a409c9 100644
--- a/ash/drag_drop/drag_drop_controller.h
+++ b/ash/drag_drop/drag_drop_controller.h
@@ -8,6 +8,7 @@
 #include <memory>
 
 #include "ash/ash_export.h"
+#include "ash/display/window_tree_host_manager.h"
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ -35,7 +36,8 @@ class DragDropControllerTest;
 class ASH_EXPORT DragDropController : public aura::client::DragDropClient,
                                       public ui::EventHandler,
                                       public gfx::AnimationDelegate,
-                                      public aura::WindowObserver {
+                                      public aura::WindowObserver,
+                                      public WindowTreeHostManager::Observer {

[msw, 2016/08/05 19:32:58]

nit: use ash/common/wm_display_observer.h instead?
(even though we might not really converting this directly?)

[James Cook, 2016/08/05 20:10:11]

Done.

  public:
   DragDropController();
   ~DragDropController() override;
@@ -85,6 +87,9 @@ class ASH_EXPORT DragDropController : public aura::client::DragDropClient,
   void AnimationProgressed(const gfx::Animation* animation) override;
   void AnimationCanceled(const gfx::Animation* animation) override;
 
+  // WindowTreeHostManager::Observer:
+  void OnDisplayConfigurationChanging() override;
+
   // Helper method to start drag widget flying back animation.
   void StartCanceledAnimation(int animation_duration_ms);