Enable virtual keyboard in overview mode

ash/virtual_keyboard_observer.cc

Index: ash/virtual_keyboard_observer.cc
diff --git a/ash/virtual_keyboard_observer.cc b/ash/virtual_keyboard_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bb551c51d96e9257717a46f83f41362820c8b3ed
--- /dev/null
+++ b/ash/virtual_keyboard_observer.cc
@@ -0,0 +1,31 @@
+// 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.
+
+#include "ash/virtual_keyboard_observer.h"
+
+#include "ash/shell.h"
+#include "ui/keyboard/keyboard_util.h"
+
+namespace ash {
+
+VirtualKeyboardObserver::VirtualKeyboardObserver() {
+  Shell::GetInstance()->AddShellObserver(this);
+}
+
+VirtualKeyboardObserver::~VirtualKeyboardObserver() {
+  Shell::GetInstance()->RemoveShellObserver(this);
+}
+
+void VirtualKeyboardObserver::OnMaximizeModeStarted() {
+  keyboard::SetTouchKeyboardEnabled(true);
+  Shell::GetInstance()->CreateKeyboard();
+}
+
+void VirtualKeyboardObserver::OnMaximizeModeEnded() {
+  keyboard::SetTouchKeyboardEnabled(false);
+  if (!keyboard::IsKeyboardEnabled())
+    Shell::GetInstance()->DeactivateKeyboard();
+}
+
+}  // namespace ash