Nix GetRootWindowController, use RootWindowController::ForWindow.

ash/root_window_controller.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_ROOT_WINDOW_CONTROLLER_H_
 #define ASH_ROOT_WINDOW_CONTROLLER_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 62 matching lines @@
 namespace wm {
 class RootWindowLayoutManager;
 }
 
 // This class maintains the per root window state for ash. This class
 // owns the root window and other dependent objects that should be
 // deleted upon the deletion of the root window. This object is
 // indirectly owned and deleted by |WindowTreeHostManager|.
 // The RootWindowController for particular root window is stored in
 // its property (RootWindowSettings) and can be obtained using
-// |GetRootWindowController(aura::WindowEventDispatcher*)| function.
+// |RootWindowController::ForWindow(aura::Window*)| function.
 class ASH_EXPORT RootWindowController : public ShellObserver {
  public:
   // Enumerates the type of display. If there is only a single display then
   // it is primary. In a multi-display environment one monitor is deemed the
   // PRIMARY and all others SECONDARY.
   enum class RootWindowType { PRIMARY, SECONDARY };
 
   ~RootWindowController() override;
 
   // Creates and Initialize the RootWindowController for primary display.
@@ skipping 274 matching lines @@
   // Handles double clicks on the panel window header.
   std::unique_ptr<ui::EventHandler> panel_container_handler_;
 
   std::unique_ptr<::wm::ScopedCaptureClient> capture_client_;
 
   static std::vector<RootWindowController*>* root_window_controllers_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowController);
 };
 
-// On classic ash, returns the RootWindowController for the given |root_window|.
-// On mus ash, returns the RootWindowController for the primary display.
-// See RootWindowController class comment above.
-ASH_EXPORT RootWindowController* GetRootWindowController(
-    const aura::Window* root_window);
-
 }  // namespace ash
 
 #endif  // ASH_ROOT_WINDOW_CONTROLLER_H_