Linux: fix a bunch of NULL vs. 0 issues spotted by gcc 4.5.

chrome/browser/automation/automation_provider_observers.cc

 // Copyright (c) 2010 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 "chrome/browser/automation/automation_provider_observers.h"
 
 #include <deque>
 #include <string>
 #include <vector>
 
@@ skipping 1412 matching lines @@
   delete this;
 }
 
 NTPInfoObserver::NTPInfoObserver(
     AutomationProvider* automation,
     IPC::Message* reply_message,
     CancelableRequestConsumer* consumer)
         : automation_(automation),
           reply_message_(reply_message),
           consumer_(consumer),
-          request_(NULL),
+          request_(0),
           ntp_info_(new DictionaryValue) {
   top_sites_ = automation_->profile()->GetTopSites();
   if (!top_sites_) {
     AutomationJSONReply(automation_, reply_message_)
         .SendError("Profile does not have service for querying the top sites.");
     return;
   }
   TabRestoreService* service = automation_->profile()->GetTabRestoreService();
   if (!service) {
     AutomationJSONReply(automation_, reply_message_)
@@ skipping 185 matching lines @@
                  NotificationService::AllSources());
 }
 
 void RendererProcessClosedObserver::Observe(
     NotificationType type,
     const NotificationSource& source,
     const NotificationDetails& details) {
   AutomationJSONReply(automation_, reply_message_).SendSuccess(NULL);
   delete this;
 }