status_icons: Factor out status icon observer into its own header file.

chrome/browser/status_icons/status_icon_observer.h

+// Copyright (c) 2012 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 CHROME_BROWSER_STATUS_ICONS_STATUS_ICON_OBSERVER_H_
+#define CHROME_BROWSER_STATUS_ICONS_STATUS_ICON_OBSERVER_H_
+#pragma once
+
+class StatusIconObserver {
+ public:
+  // Called when the user clicks on the system tray icon. Clicks that result
+  // in the context menu being displayed will not be passed to this observer
+  // (i.e. if there's a context menu set on this status icon, and the user
+  // right clicks on the icon to display the context menu, OnClicked will not

[Andrew T Wilson (Slow), 2012/05/22 00:53:56]

nit: OnClicked->OnStatusIconClicked()

[tfarina, 2012/05/23 14:58:08]

Done.

+  // be called).
+  // Note: Chrome OS displays the context menu on left button clicks.
+  // This will only be fired for this platform if no context menu is present.
+  virtual void OnStatusIconClicked() = 0;
+
+ protected:
+  virtual ~StatusIconObserver() {}
+};
+
+#endif  // CHROME_BROWSER_STATUS_ICONS_STATUS_ICON_OBSERVER_H_