Add skeleton implementation of ExtensionPushMessagingEventRouter.

chrome/browser/extensions/api/push_messaging/invalidation_handler_observer.h

Index: chrome/browser/extensions/api/push_messaging/invalidation_handler_observer.h
diff --git a/chrome/browser/extensions/api/push_messaging/invalidation_handler_observer.h b/chrome/browser/extensions/api/push_messaging/invalidation_handler_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..f1f42f23974333c191f93348334f9cc7bd9be5fb
--- /dev/null
+++ b/chrome/browser/extensions/api/push_messaging/invalidation_handler_observer.h
@@ -0,0 +1,25 @@
+// 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_API_PUSH_MESSAGING_INVALIDATION_HANDLER_OBSERVER_H_
+#define CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_INVALIDATION_HANDLER_OBSERVER_H_
+
+#include <string>
+
+namespace extensions {
+
+// Observer interface for the push messaging invalidation handler. For each
+// object that was invalidated, OnMessage() will be called back once for that
+// object.
+class InvalidationHandlerObserver {
+ public:
+  virtual ~InvalidationHandlerObserver() {}
+  virtual void OnMessage(const std::string& extension_id,
+                         int subchannel,
+                         const std::string& payload) = 0;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_PUSH_MESSAGING_INVALIDATION_HANDLER_OBSERVER_H_