Converts MaximizeModeWindowManager to use ash/common types

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 facf5699e80b777c790fe6d07af80b46ab20a26c..ad26b546c2cfe77cea17b552a00d7e5d4b023713 100644
--- a/ash/common/wm_root_window_controller.h
+++ b/ash/common/wm_root_window_controller.h
@@ -20,6 +20,7 @@ class WmShelf;
 class WmShell;
 class WmRootWindowControllerObserver;
 class WmWindow;
+class WorkspaceLayoutManagerBackdropDelegate;
 
 // Provides state associated with a root of a window hierarchy.
 class ASH_EXPORT WmRootWindowController {
@@ -32,6 +33,11 @@ class ASH_EXPORT WmRootWindowController {
 
   virtual wm::WorkspaceWindowState GetWorkspaceWindowState() = 0;
 
+  // TODO: remove when WorkspaceController moved to common:
+  // http://crbug.com/624173.
+  virtual void SetMaximizeBackdropDelegate(
+      std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate> delegate) = 0;
+
   virtual AlwaysOnTopController* GetAlwaysOnTopController() = 0;
 
   virtual WmShelf* GetShelf() = 0;