Removes WmRootWindowController subclasses

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 86d2677f286c910c9d2db731e2ee68e7e8664e59..723d969c4236d4bb0adcdf34978b2199eaef67a1 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -26,6 +26,7 @@
 namespace aura {
 class RootWindow;
 class Window;
+class WindowTreeClient;
 namespace client {
 class ActivationClient;
 class FocusClient;
@@ -184,6 +185,15 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   static const aura::Window* GetContainer(const aura::Window* root_window,
                                           int container_id);
 
+  // TODO(sky): better isolate this.
+  static void set_window_tree_client(aura::WindowTreeClient* client) {
+    window_tree_client_ = client;
+  }
+
+  static aura::WindowTreeClient* window_tree_client() {
+    return window_tree_client_;
+  }
+
   // Creates a default views::NonClientFrameView for use by windows in the
   // Ash environment.
   views::NonClientFrameView* CreateDefaultNonClientFrameView(
@@ -414,6 +424,9 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
 
   static Shell* instance_;
 
+  // Only valid in mash, for classic ash this is null.
+  static aura::WindowTreeClient* window_tree_client_;
+
   // If set before the Shell is initialized, the mouse cursor will be hidden
   // when the screen is initially created.
   static bool initially_hide_cursor_;