mash: Remove WmRootWindowControllerObserver.

ash/common/wm_root_window_controller.h

Index: ash/common/wm_root_window_controller.h
diff --git a/ash/common/wm_root_window_controller.h b/ash/common/wm_root_window_controller.h
index c897fdd7e1ee17a70b423611196dbc79b452037d..e190072a1199d91c16f1939975804278c3085ab5 100644
--- a/ash/common/wm_root_window_controller.h
+++ b/ash/common/wm_root_window_controller.h
@@ -8,7 +8,6 @@
 #include "ash/ash_export.h"
 #include "ash/common/wm/workspace/workspace_types.h"
 #include "base/macros.h"
-#include "base/observer_list.h"
 #include "ui/views/widget/widget.h"
 
 namespace gfx {
@@ -20,7 +19,6 @@ namespace ash {
 class AlwaysOnTopController;
 class WmShelf;
 class WmShell;
-class WmRootWindowControllerObserver;
 class WmWindow;
 class WorkspaceController;
 
@@ -44,9 +42,6 @@ class ASH_EXPORT WmRootWindowController {
 
   wm::WorkspaceWindowState GetWorkspaceWindowState();
 
-  void AddObserver(WmRootWindowControllerObserver* observer);
-  void RemoveObserver(WmRootWindowControllerObserver* observer);
-
   virtual bool HasShelf() = 0;
 
   virtual WmShell* GetShell() = 0;
@@ -85,10 +80,6 @@ class ASH_EXPORT WmRootWindowController {
 
   void DeleteWorkspaceController();
 
-  base::ObserverList<WmRootWindowControllerObserver>* observers() {
-    return &observers_;
-  }
-
  private:
   WmWindow* root_;
 
@@ -96,8 +87,6 @@ class ASH_EXPORT WmRootWindowController {
 
   std::unique_ptr<WorkspaceController> workspace_controller_;
 
-  base::ObserverList<WmRootWindowControllerObserver> observers_;
-
   DISALLOW_COPY_AND_ASSIGN(WmRootWindowController);
 };