Reland "Add a full screen virtual keyboard to virtual keyboard root window"

ash/display/display_controller.h

Index: ash/display/display_controller.h
diff --git a/ash/display/display_controller.h b/ash/display/display_controller.h
index 9dc20f5d34bfb73f525e841d2f521ade056e6b5e..75fe22cd473156d2de5cf1e6f048e1fc1341ed09 100644
--- a/ash/display/display_controller.h
+++ b/ash/display/display_controller.h
@@ -84,6 +84,11 @@ class ASH_EXPORT DisplayController : public gfx::DisplayObserver,
     return mirror_window_controller_.get();
   }
 
+  internal::VirtualKeyboardWindowController*
+      virtual_keyboard_window_controller() {
+    return virtual_keyboard_window_controller_.get();
+  }
+
   // Initializes primary display.
   void InitPrimaryDisplay();