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/extensions/pending_extension_manager.cc b/chrome/browser/extensions/pending_extension_manager.cc
index d07170bc..c11ebf8 100644
--- a/chrome/browser/extensions/pending_extension_manager.cc
+++ b/chrome/browser/extensions/pending_extension_manager.cc
@@ -9,6 +9,8 @@
 #include "chrome/common/extensions/extension.h"
 #include "content/public/browser/browser_thread.h"
 
+using content::BrowserThread;
+
 namespace {
 
 // Install predicate used by AddFromExternalUpdateUrl().