Add scopedallowIO for google chrome specific registry access.

chrome/installer/util/google_update_settings.cc

 // Copyright (c) 2012 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/installer/util/google_update_settings.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/path_service.h"
@@ skipping 111 matching lines @@
 }
 
 bool GetChromeChannelInternal(bool system_install,
                               bool add_multi_modifier,
                               string16* channel) {
   BrowserDistribution* dist = BrowserDistribution::GetDistribution();
   if (dist->GetChromeChannel(channel)) {
     return true;
   }
 
+  // The registry functions below will end up going to disk.  Do this on another
+  // thread to avoid slowing the IO thread.  http://crbug.com/62121
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
+
   HKEY root_key = system_install ? HKEY_LOCAL_MACHINE : HKEY_CURRENT_USER;
   string16 reg_path = dist->GetStateKey();
   RegKey key(root_key, reg_path.c_str(), KEY_READ);
 
   installer::ChannelInfo channel_info;
   if (!channel_info.Initialize(key)) {
     channel->assign(installer::kChromeChannelUnknown);
     return false;
   }
 
@@ skipping 395 matching lines @@
   string16 cmd_line;
   RegKey update_key;
 
   if (update_key.Open(root_key, google_update::kRegPathGoogleUpdate,
                       KEY_QUERY_VALUE) == ERROR_SUCCESS) {
     update_key.ReadValue(google_update::kRegUninstallCmdLine, &cmd_line);
   }
 
   return cmd_line;
 }