Do not activate system tray bubble by default

ash/common/key_event_watcher.cc

Index: ash/common/key_event_watcher.cc
diff --git a/ash/common/key_event_watcher.cc b/ash/common/key_event_watcher.cc
new file mode 100644
index 0000000000000000000000000000000000000000..cf3d368c8c66909d41e63ba54476cac857ca991a
--- /dev/null
+++ b/ash/common/key_event_watcher.cc
@@ -0,0 +1,27 @@
+// Copyright 2016 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/common/key_event_watcher.h"
+
+namespace ash {
+
+KeyEventWatcher::KeyEventWatcher() {}
+
+KeyEventWatcher::~KeyEventWatcher() {}
+
+void KeyEventWatcher::AddKeyEventCallback(const ui::Accelerator& key,
+                                          const KeyEventCallback& callback) {
+  callback_map_.insert(std::make_pair(key, callback));
+}
+
+bool KeyEventWatcher::HandleKeyEvent(const ui::KeyEvent& event) {
+  auto iter = callback_map_.find(ui::Accelerator(event));
+  if (iter != callback_map_.end()) {
+    iter->second.Run(event);
+    return true;
+  }
+  return false;
+}
+
+}  // namespace ash