Support chrome.windows extension API events for browserless Panels.

chrome/browser/extensions/window_controller_list_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_EXTENSIONS_WINDOW_CONTROLLER_LIST_OBSERVER_H_
+#define CHROME_BROWSER_EXTENSIONS_WINDOW_CONTROLLER_LIST_OBSERVER_H_
+
+namespace extensions {
+
+class WindowController;
+
+// Implementations must not change the contents of the WindowControllerList
+// inside any of these methods.
+class WindowControllerListObserver {
+  public:
+  // Called immediately after a window controller is added to the list
+  virtual void OnWindowControllerAdded(WindowController* window_controller) {}
+
+  // Called immediately after a window controller is removed from the list
+  virtual void OnWindowControllerRemoved(WindowController* window_controller) {}
+
+ protected:
+  virtual ~WindowControllerListObserver() {}
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_WINDOW_CONTROLLER_LIST_OBSERVER_H_