Remove an explicit call from the NavigationController to the alternate URL

fetcher since there is already a notification that does this.

I created a class that will automatically unregister for notifications when it
goes out of scope and used it here. I think it will be useful for most consumers
of notifications.
Review URL: http://codereview.chromium.org/2895

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@2276 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 63 insertions, 0 deletions

diff --git a/chrome/common/notification_registrar.h b/chrome/common/notification_registrar.h
new file mode 100644
index 0000000..e253eb4
--- /dev/null
+++ b/chrome/common/notification_registrar.h
@@ -0,0 +1,63 @@
+// Copyright (c) 2006-2008 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_COMMON_NOTIFICATION_REGISTRAR_H_
+#define CHROME_COMMON_NOTIFICATION_REGISTRAR_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "chrome/common/notification_service.h"
+
+// Aids in registering for notifications and ensures that all registered
+// notifications are unregistered when the class is destroyed.
+//
+// The intended use is that you make a NotificationRegistrar member in your
+// class and use it to register your notifications instead of going through the
+// notification service directly. It will automatically unregister them for
+// you.
+class NotificationRegistrar {
+ public:
+  // This class must not be derived from (we don't have a virtual destructor so
+  // it won't work). Instead, use it as a member in your class.
+  NotificationRegistrar();
+  ~NotificationRegistrar();
+
+  // Wrappers around NotificationService::[Add|Remove]Observer.
+  void Add(NotificationObserver* observer,
+           NotificationType type,
+           NotificationSource source);
+  void Remove(NotificationObserver* observer,
+              NotificationType type,
+              NotificationSource source);
+
+  // Unregisters all notifications.
+  void RemoveAll();
+
+ private:
+  struct Record {
+    bool operator==(const Record& other) const {
+      return observer == other.observer &&
+             type == other.type &&
+             source == other.source;
+    }
+
+    NotificationObserver* observer;
+    NotificationType type;
+    NotificationSource source;
+  };
+
+  // We keep registered notifications in a simple vector. This means we'll do
+  // brute-force searches when removing them individually, but individual
+  // removal is uncommon, and there will typically only be a couple of
+  // notifications anyway.
+  typedef std::vector<Record> RecordVector;
+
+  // Lists all notifications we're currently registered for.
+  RecordVector registered_;
+
+  DISALLOW_COPY_AND_ASSIGN(NotificationRegistrar);
+};
+
+#endif  // CHROME_COMMON_NOTIFICATION_REGISTRAR_H_