chromeos: Add SurfaceServiceProvider.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 86382cd8806c079025e9822dfdcd9261c330fe32..806b176e9c6a3b4e9ea449c704c9ecbe2b84544f 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -136,6 +136,7 @@ class ShellObserver;
 class SlowAnimationEventFilter;
 class StatusAreaWidget;
 class StickyKeysController;
+class SurfaceController;
 class SystemGestureEventFilter;
 class SystemModalContainerEventFilter;
 class SystemTray;
@@ -521,6 +522,8 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
     return maximize_mode_controller_.get();
   }
 
+  SurfaceController* surface_controller() { return surface_controller_.get(); }
+
 #if defined(OS_CHROMEOS)
   // TODO(oshima): Move these objects to WindowTreeHostManager.
   ui::DisplayConfigurator* display_configurator() {
@@ -748,6 +751,8 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
 
   scoped_ptr<MaximizeModeController> maximize_mode_controller_;
 
+  scoped_ptr<SurfaceController> surface_controller_;
+
   // |native_cursor_manager_| is owned by |cursor_manager_|, but we keep a
   // pointer to vend to test code.
   AshNativeCursorManager* native_cursor_manager_;