Fixes crash for operations on non-existing notifications.

ui/message_center/message_center_impl.cc

 // Copyright (c) 2013 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 "ui/message_center/message_center_impl.h"
 
 #include "base/observer_list.h"
 #include "ui/message_center/message_center_observer.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_list.h"
@@ skipping 94 matching lines @@
     const string16& message,
     const base::DictionaryValue* optional_fields) {
   notification_list_->UpdateNotificationMessage(
       old_id, new_id, title, message, optional_fields);
   FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                     OnNotificationUpdated(new_id));
 }
 
 void MessageCenterImpl::RemoveNotification(const std::string& id,
                                            bool by_user) {
+  if (!HasNotification(id))
+    return;
+
   // In many cases |id| is a reference to an existing notification instance
   // but the instance can be destructed in RemoveNotification(). Hence
   // copies the id explicitly here.
   std::string copied_id(id);
   notification_list_->RemoveNotification(copied_id);
   FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                     OnNotificationRemoved(copied_id, by_user));
 }
 
 void MessageCenterImpl::RemoveAllNotifications(bool by_user) {
@@ skipping 25 matching lines @@
                                          const gfx::Image& image) {
   if (notification_list_->SetNotificationImage(notification_id, image)) {
     FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                       OnNotificationUpdated(notification_id));
   }
 }
 
 void MessageCenterImpl::SetNotificationButtonIcon(
     const std::string& notification_id, int button_index,
     const gfx::Image& image) {
+  if (!HasNotification(notification_id))
+    return;
   if (notification_list_->SetNotificationButtonIcon(notification_id,
                                                     button_index, image)) {
     FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                       OnNotificationUpdated(notification_id));
   }
 }
 
 void MessageCenterImpl::DisableNotificationsByExtension(
     const std::string& id) {
   if (delegate_)
@@ skipping 28 matching lines @@
     delegate_->ShowSettings(id);
 }
 
 void MessageCenterImpl::ShowNotificationSettingsDialog(
     gfx::NativeView context) {
   if (delegate_)
     delegate_->ShowSettingsDialog(context);
 }
 
 void MessageCenterImpl::ExpandNotification(const std::string& id) {
+  if (!HasNotification(id))
+    return;
   notification_list_->MarkNotificationAsExpanded(id);
   FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                     OnNotificationUpdated(id));
 }
 
 void MessageCenterImpl::ClickOnNotification(const std::string& id) {
+  if (!HasNotification(id))
+    return;
   if (HasPopupNotifications())
     MarkSinglePopupAsShown(id, true);
   FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                     OnNotificationClicked(id));
 }
 
 void MessageCenterImpl::ClickOnNotificationButton(const std::string& id,
                                               int button_index) {
+  if (!HasNotification(id))
+    return;
   if (HasPopupNotifications())
     MarkSinglePopupAsShown(id, true);
   FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                     OnNotificationButtonClicked(id, button_index));
 }
 
 void MessageCenterImpl::MarkSinglePopupAsShown(const std::string& id,
                                                bool mark_notification_as_read) {
+  if (!HasNotification(id))
+    return;
   notification_list_->MarkSinglePopupAsShown(id, mark_notification_as_read);
   FOR_EACH_OBSERVER(MessageCenterObserver, observer_list_,
                     OnNotificationUpdated(id));
 }
 
 void MessageCenterImpl::SetQuietMode(bool in_quiet_mode) {
   notification_list_->SetQuietMode(in_quiet_mode);
 }
 
 void MessageCenterImpl::EnterQuietModeWithExpire(
     const base::TimeDelta& expires_in) {
   notification_list_->EnterQuietModeWithExpire(expires_in);
 }
 
 }  // namespace message_center