Lazily initialize MessageLoop for faster thread startup

chrome/browser/io_thread.cc

Index: chrome/browser/io_thread.cc
diff --git a/chrome/browser/io_thread.cc b/chrome/browser/io_thread.cc
index 097e8a67ddc54ddc1b8c0879683e4bc0dbb0ec82..e163dc8db13ea1778f94cb897ffa691d577f05c2 100644
--- a/chrome/browser/io_thread.cc
+++ b/chrome/browser/io_thread.cc
@@ -614,11 +614,6 @@ net::URLRequestContextGetter* IOThread::system_url_request_context_getter() {
 }
 
 void IOThread::Init() {
-  // Prefer to use InitAsync unless you need initialization to block
-  // the UI thread
-}
-
-void IOThread::InitAsync() {
   // TODO(erikchen): Remove ScopedTracker below once http://crbug.com/466432
   // is fixed.
   tracked_objects::ScopedTracker tracking_profile1(