Merges RootWindowControllerCommon into WmRootWindowController

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index 740d0802083fd91f3f2b2808949effa88ec2f419..2f26f0dff61c741c0953f5b3c5bc2a5c6f0dec73 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -55,7 +55,6 @@ class AnimatingWallpaperWidgetController;
 class DockedWindowLayoutManager;
 enum class LoginStatus;
 class PanelLayoutManager;
-class RootWindowControllerCommon;
 class Shelf;
 class ShelfLayoutManager;
 class ShelfWidget;
@@ -67,6 +66,7 @@ class SystemWallpaperController;
 class TouchHudDebug;
 class TouchHudProjection;
 class WallpaperWidgetController;
+class WmRootWindowControllerAura;
 class WmShelfAura;
 class WmWindow;
 class WorkspaceController;
@@ -270,7 +270,8 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
 
   std::unique_ptr<AshWindowTreeHost> ash_host_;
 
-  std::unique_ptr<RootWindowControllerCommon> root_window_controller_common_;
+  // Owned by the root window.
+  WmRootWindowControllerAura* wm_root_window_controller_ = nullptr;
 
   std::unique_ptr<StackingController> stacking_controller_;