Remove linked_ptr from ash

ash/wm/resize_shadow_controller.h

Index: ash/wm/resize_shadow_controller.h
diff --git a/ash/wm/resize_shadow_controller.h b/ash/wm/resize_shadow_controller.h
index 0c651e050ad379f5731d6775d05c66a7aaddab3d..cd07058aeda2b8f66369b39329911ac11ab07ca7 100644
--- a/ash/wm/resize_shadow_controller.h
+++ b/ash/wm/resize_shadow_controller.h
@@ -6,11 +6,11 @@
 #define ASH_WM_RESIZE_SHADOW_CONTROLLER_H_
 
 #include <map>
+#include <memory>
 
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
-#include "base/memory/linked_ptr.h"
 #include "ui/aura/window_observer.h"
 
 namespace aura {
@@ -42,8 +42,6 @@ class ASH_EXPORT ResizeShadowController : public aura::WindowObserver {
   void OnWindowDestroyed(aura::Window* window) override;
 
  private:
-  typedef std::map<aura::Window*, linked_ptr<ResizeShadow>> WindowShadowMap;
-
   // Creates a shadow for a given window and returns it.  |window_shadows_|
   // owns the memory.
   ResizeShadow* CreateShadow(aura::Window* window);
@@ -51,7 +49,7 @@ class ASH_EXPORT ResizeShadowController : public aura::WindowObserver {
   // Returns the resize shadow for |window| or NULL if no shadow exists.
   ResizeShadow* GetShadowForWindow(aura::Window* window);
 
-  WindowShadowMap window_shadows_;
+  std::map<aura::Window*, std::unique_ptr<ResizeShadow>> window_shadows_;
 
   DISALLOW_COPY_AND_ASSIGN(ResizeShadowController);
 };