Move PageTransition into content namespace. While I'm touching all these files, I've also updated...

content/browser/download/mhtml_generation_manager.cc

 // Copyright (c) 2011 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 "content/browser/download/mhtml_generation_manager.h"
 
 #include "base/platform_file.h"
 #include "content/browser/renderer_host/render_process_host.h"
 #include "content/browser/renderer_host/render_view_host.h"
 #include "content/browser/tab_contents/tab_contents.h"
 #include "content/common/content_notification_types.h"
 #include "content/common/notification_service.h"
-#include "content/common/page_transition_types.h"
 #include "content/common/view_messages.h"
 
 MHTMLGenerationManager::Job::Job()
     : browser_file(base::kInvalidPlatformFileValue),
       renderer_file(IPC::InvalidPlatformFileForTransit()),
       process_id(-1),
       routing_id(-1) {
 }
 
 MHTMLGenerationManager::MHTMLGenerationManager() {
@@ skipping 100 matching lines @@
       NewRunnableMethod(this, &MHTMLGenerationManager::CloseFile,
                         job.browser_file));
 
   id_to_job_.erase(job_id);
 }
 
 void MHTMLGenerationManager::CloseFile(base::PlatformFile file) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   base::ClosePlatformFile(file);
 }