Revert of Reland: Lazily initialize MessageLoop for faster thread startup

content/public/test/test_browser_thread.h

Index: content/public/test/test_browser_thread.h
diff --git a/content/public/test/test_browser_thread.h b/content/public/test/test_browser_thread.h
index d3a256474e36c40814ab9037a8def9c10a39ba2f..2428bbb66ba729f3a61c33056d3d0a581ff5957b 100644
--- a/content/public/test/test_browser_thread.h
+++ b/content/public/test/test_browser_thread.h
@@ -36,10 +36,6 @@
   // Starts the thread with a generic message loop.
   bool Start();
 
-  // Starts the thread with a generic message loop and waits for the
-  // thread to run.
-  bool StartAndWaitForTesting();
-
   // Starts the thread with an IOThread message loop.
   bool StartIOThread();