Enable virtual keyboard in overview mode

ash/virtual_keyboard_controller.h

Index: ash/virtual_keyboard_controller.h
diff --git a/ash/virtual_keyboard_controller.h b/ash/virtual_keyboard_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..47ef475c9b6ef0015d713592cdfb48cbb8e7b1bf
--- /dev/null
+++ b/ash/virtual_keyboard_controller.h
@@ -0,0 +1,29 @@
+// Copyright 2014 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_VIRTUAL_KEYBOARD_CONTROLLER_H_
+#define ASH_VIRTUAL_KEYBOARD_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "ash/shell_observer.h"
+
+namespace ash {
+
+// This class observes enter/leaving maximized mode for virtual keyboard.
+class ASH_EXPORT VirtualKeyboardController : public ShellObserver {
+ public:
+  VirtualKeyboardController();
+  virtual ~VirtualKeyboardController();
+
+  // ShellObserver:
+  virtual void OnMaximizeModeStarted() OVERRIDE;
+  virtual void OnMaximizeModeEnded() OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(VirtualKeyboardController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_VIRTUAL_KEYBOARD_CONTROLLER_H_