Thread IO safety: file_util annotated, IO thread blocked from doing IO

chrome/browser/net/url_request_mock_util.cc

 // Copyright (c) 2009 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/net/url_request_mock_util.h"
 
 #include <string>
 
 #include "base/path_service.h"
+#include "base/thread_restrictions.h"
 #include "chrome/browser/browser_thread.h"
 #include "chrome/browser/net/url_request_failed_dns_job.h"
 #include "chrome/browser/net/url_request_mock_http_job.h"
 #include "chrome/browser/net/url_request_mock_link_doctor_job.h"
 #include "chrome/browser/net/url_request_slow_download_job.h"
 #include "chrome/browser/net/url_request_slow_http_job.h"
 #include "chrome/common/chrome_paths.h"
 #include "net/url_request/url_request_filter.h"
 
 namespace chrome_browser_net {
 
 void SetUrlRequestMocksEnabled(bool enabled) {
   // Since this involves changing the URLRequest ProtocolFactory, we need to
   // run on the IO thread.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   if (enabled) {
+    // We have to look around for our helper files, but we only use
+    // this from tests, so allow these IO operations to happen
+    // anywhere.
+    base::ThreadRestrictions::ScopedAllowIO allow_io;
+
     URLRequestFilter::GetInstance()->ClearHandlers();
 
     URLRequestFailedDnsJob::AddUrlHandler();
     URLRequestMockLinkDoctorJob::AddUrlHandler();
     URLRequestSlowDownloadJob::AddUrlHandler();
 
     FilePath root_http;
     PathService::Get(chrome::DIR_TEST_DATA, &root_http);
     URLRequestMockHTTPJob::AddUrlHandler(root_http);
     URLRequestSlowHTTPJob::AddUrlHandler(root_http);
   } else {
     // Revert to the default handlers.
     URLRequestFilter::GetInstance()->ClearHandlers();
   }
 }
 
 }  // namespace chrome_browser_net