Lazily initialize MessageLoop for faster thread startup

content/public/test/test_browser_thread.cc

Index: content/public/test/test_browser_thread.cc
diff --git a/content/public/test/test_browser_thread.cc b/content/public/test/test_browser_thread.cc
index ac67480fe5cd36b6cd515d866656e2687983a9f1..62d9eb84534033756d7b3bc649f41b0bdef2cc25 100644
--- a/content/public/test/test_browser_thread.cc
+++ b/content/public/test/test_browser_thread.cc
@@ -58,6 +58,10 @@ bool TestBrowserThread::Start() {
   return impl_->Start();
 }
 
+bool TestBrowserThread::StartAndWaitForTesting() {
+  return impl_->StartAndWaitForTesting();
+}
+
 bool TestBrowserThread::StartIOThread() {
   base::Thread::Options options;
   options.message_loop_type = base::MessageLoop::TYPE_IO;