Move BrowserThread to content namespace.

TBR=owners
BUG=98716

Review URL: http://codereview.chromium.org/8437002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@108270 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/browsing_data_appcache_helper.cc b/chrome/browser/browsing_data_appcache_helper.cc
index f88e21e..b30fbb4 100644
--- a/chrome/browser/browsing_data_appcache_helper.cc
+++ b/chrome/browser/browsing_data_appcache_helper.cc
@@ -13,6 +13,7 @@
 #include "webkit/appcache/appcache_storage.h"
 
 using appcache::AppCacheDatabase;
+using content::BrowserThread;
 
 BrowsingDataAppCacheHelper::BrowsingDataAppCacheHelper(Profile* profile)
     : is_fetching_(false),