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, 54 insertions, 0 deletions

diff --git a/chrome/common/notification_registrar.cc b/chrome/common/notification_registrar.cc
new file mode 100644
index 0000000..fdedde4
--- /dev/null
+++ b/chrome/common/notification_registrar.cc
@@ -0,0 +1,54 @@
+// 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.
+
+#include <algorithm>
+
+#include "chrome/common/notification_registrar.h"
+
+NotificationRegistrar::NotificationRegistrar() {
+}
+
+NotificationRegistrar::~NotificationRegistrar() {
+  RemoveAll();
+}
+
+void NotificationRegistrar::Add(NotificationObserver* observer,
+                                NotificationType type,
+                                NotificationSource source) {
+  Record record = { observer, type, source };
+  DCHECK(std::find(registered_.begin(), registered_.end(), record) ==
+         registered_.end()) << "Duplicate registration.";
+  registered_.push_back(record);
+
+  NotificationService::current()->AddObserver(observer, type, source);
+}
+
+void NotificationRegistrar::Remove(NotificationObserver* observer,
+                                   NotificationType type,
+                                   NotificationSource source) {
+  Record record = { observer, type, source };
+  RecordVector::iterator found = std::find(
+      registered_.begin(), registered_.end(), record);
+  if (found != registered_.end()) {
+    registered_.erase(found);
+  } else {
+    // Fall through to passing the removal through to the notification service.
+    // If it really isn't registered, it will also assert and do nothing, but
+    // we might as well catch the case where the class is trying to unregister
+    // for something they registered without going through us.
+    NOTREACHED();
+  }
+
+  NotificationService::current()->RemoveObserver(observer, type, source);
+}
+
+void NotificationRegistrar::RemoveAll() {
+  NotificationService* service = NotificationService::current();
+  for (size_t i = 0; i < registered_.size(); i++) {
+    service->RemoveObserver(registered_[i].observer,
+                            registered_[i].type,
+                            registered_[i].source);
+  }
+  registered_.clear();
+}