Refactors DockedWindowLayoutManager in terms of ash/wm/common

ash/wm/common/wm_root_window_controller.h

Index: ash/wm/common/wm_root_window_controller.h
diff --git a/ash/wm/common/wm_root_window_controller.h b/ash/wm/common/wm_root_window_controller.h
index d8a1018e4b201af2a3158da82f9c4965f18aeb2e..1c263b1d695c420c7f5923740b839565ecaedbe2 100644
--- a/ash/wm/common/wm_root_window_controller.h
+++ b/ash/wm/common/wm_root_window_controller.h
@@ -16,6 +16,7 @@ namespace wm {
 
 class WmGlobals;
 class WmRootWindowControllerObserver;
+class WmShelf;
 class WmWindow;
 
 // Provides state associated with a root of a window hierarchy.
@@ -31,6 +32,8 @@ class ASH_EXPORT WmRootWindowController {
 
   virtual WorkspaceWindowState GetWorkspaceWindowState() = 0;
 
+  virtual WmShelf* GetShelf() = 0;
+
   // Returns the window associated with this WmRootWindowController.
   virtual WmWindow* GetWindow() = 0;