Lazily initialize MessageLoop for faster thread startup

chrome/browser/metrics/thread_watcher_unittest.cc

Index: chrome/browser/metrics/thread_watcher_unittest.cc
diff --git a/chrome/browser/metrics/thread_watcher_unittest.cc b/chrome/browser/metrics/thread_watcher_unittest.cc
index 4b3c457a36baa839dd65c3b6b9161fc88d152adc..00171b8052257fba0f31b0854d259b2b9fb5df30 100644
--- a/chrome/browser/metrics/thread_watcher_unittest.cc
+++ b/chrome/browser/metrics/thread_watcher_unittest.cc
@@ -257,9 +257,9 @@ class ThreadWatcherTest : public ::testing::Test {
     db_thread_.reset(new content::TestBrowserThread(BrowserThread::DB));
     io_thread_.reset(new content::TestBrowserThread(BrowserThread::IO));
     watchdog_thread_.reset(new WatchDogThread());
-    db_thread_->Start();
-    io_thread_->Start();
-    watchdog_thread_->Start();
+    db_thread_->StartAndWaitForTesting();
+    io_thread_->StartAndWaitForTesting();
+    watchdog_thread_->StartAndWaitForTesting();
 
     WatchDogThread::PostTask(
         FROM_HERE,
@@ -691,7 +691,7 @@ TEST_F(ThreadWatcherListTest, Restart) {
   content::TestBrowserThread ui_thread(BrowserThread::UI, &message_loop_for_ui);
 
   scoped_ptr<WatchDogThread> watchdog_thread_(new WatchDogThread());
-  watchdog_thread_->Start();
+  watchdog_thread_->StartAndWaitForTesting();
 
   // See http://crbug.com/347887.
   // StartWatchingAll() will PostDelayedTask to create g_thread_watcher_list_,