Add the partial screen magnifier to Chrome OS.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 044ba06d5c4d6ba79b2fd7d444aa21cf44810819..c374d713c2c4914739d9587546d79402803d320b 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -91,6 +91,7 @@ class MouseCursorEventFilter;
 class OutputConfiguratorAnimation;
 class OverlayEventFilter;
 class PanelLayoutManager;
+class PartialMagnificationController;
 class ResizeShadowController;
 class RootWindowController;
 class RootWindowLayoutManager;
@@ -307,6 +308,10 @@ class ASH_EXPORT Shell : CursorDelegate,
     return magnification_controller_.get();
   }
 
+  internal::PartialMagnificationController* partial_magnification_controller() {
+    return partial_magnification_controller_.get();
+  }
+
   Launcher* launcher() { return launcher_.get(); }
 
   const ScreenAsh* screen() { return screen_; }
@@ -455,6 +460,8 @@ class ASH_EXPORT Shell : CursorDelegate,
   scoped_ptr<DisplayController> display_controller_;
   scoped_ptr<HighContrastController> high_contrast_controller_;
   scoped_ptr<internal::MagnificationController> magnification_controller_;
+  scoped_ptr<internal::PartialMagnificationController>
+      partial_magnification_controller_;
   scoped_ptr<aura::FocusManager> focus_manager_;
   scoped_ptr<aura::client::UserActionClient> user_action_client_;
   scoped_ptr<internal::MouseCursorEventFilter> mouse_cursor_filter_;