Add a11y virtual keyboard icon when a11y VK is enabled

ash/system/virtual_keyboard/virtual_keyboard_tray.h

Index: ash/system/virtual_keyboard/virtual_keyboard_tray.h
diff --git a/ash/system/virtual_keyboard/virtual_keyboard_tray.h b/ash/system/virtual_keyboard/virtual_keyboard_tray.h
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+++ b/ash/system/virtual_keyboard/virtual_keyboard_tray.h
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+// 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_SYSTEM_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_TRAY_H_
+#define ASH_SYSTEM_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_TRAY_H_
+
+#include "ash/system/tray/tray_background_view.h"
+#include "ash/system/tray_accessibility.h"
+#include "ash/system/user/login_status.h"
+#include "base/basictypes.h"
+#include "ui/views/controls/button/button.h"
+
+namespace views {
+class ImageButton;
+}
+
+namespace ash {
+namespace internal {
+
+class StatusAreaWidget;
+
+class VirtualKeyboardTray : public TrayBackgroundView,
+                            public views::ButtonListener,
+                            public AccessibilityObserver {
+ public:
+  explicit VirtualKeyboardTray(StatusAreaWidget* status_area_widget);
+  virtual ~VirtualKeyboardTray();
+
+  // TrayBackgroundView:
+  virtual void SetShelfAlignment(ShelfAlignment alignment) OVERRIDE;
+  virtual base::string16 GetAccessibleNameForTray() OVERRIDE;
+  virtual void HideBubbleWithView(
+      const views::TrayBubbleView* bubble_view) OVERRIDE;
+  virtual bool ClickedOutsideBubble() OVERRIDE;
+  virtual bool PerformAction(const ui::Event& event) OVERRIDE;
+
+  // views::ButtonListener:
+  virtual void ButtonPressed(views::Button* sender,
+                             const ui::Event& event) OVERRIDE;
+
+  // Overridden from AccessibilityObserver.
+  virtual void OnAccessibilityModeChanged(
+      AccessibilityNotificationVisibility notify) OVERRIDE;
+
+ private:
+  views::ImageButton* button_;  // Not owned.
+
+  DISALLOW_COPY_AND_ASSIGN(VirtualKeyboardTray);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_VIRTUAL_KEYBOARD_VIRTUAL_KEYBOARD_TRAY_H_