Move BrowserThread to content namespace.

content/browser/browser_thread_impl.cc

Index: content/browser/browser_thread_impl.cc
diff --git a/content/browser/browser_thread_impl.cc b/content/browser/browser_thread_impl.cc
index fcccb0c1dfa68fedbfb89ad81dc14658995806d1..ef5be1b0c045ce544e8cb531eb77e63322b29d6a 100644
--- a/content/browser/browser_thread_impl.cc
+++ b/content/browser/browser_thread_impl.cc
@@ -12,7 +12,7 @@
 namespace {
 
 // Friendly names for the well-known threads.
-static const char* browser_thread_names[BrowserThread::ID_COUNT] = {
+static const char* browser_thread_names[content::BrowserThread::ID_COUNT] = {
   "",  // UI (name assembled in browser_main.cc).
   "Chrome_DBThread",  // DB
   "Chrome_WebKitThread",  // WEBKIT
@@ -130,10 +130,6 @@ bool BrowserThreadImpl::PostTaskHelper(
   return !!message_loop;
 }
 
-}  // namespace content
-
-using content::BrowserThreadImpl;
-
 // TODO(joi): Remove
 DeprecatedBrowserThread::DeprecatedBrowserThread(BrowserThread::ID identifier)
     : BrowserThread(identifier) {
@@ -387,3 +383,5 @@ BrowserThread::GetMessageLoopProxyForThread(
       new BrowserThreadMessageLoopProxy(identifier));
   return proxy;
 }
+
+}  // namespace content