Fix comment to accurately reflection function names

SingleThread, not SingleTreaded (add one letter, remove two). Spelling
matters to allow searching for the referenced functions.

Change-Id: I46909856cd3540fe246d9d8a9db70aaee2ebe71f
Reviewed-on: https://chromium-review.googlesource.com/1012489
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551500}

base/threading/thread.h

@@ -29,7 +29,7 @@ class MessagePump;
 class RunLoop;
 
 // IMPORTANT: Instead of creating a base::Thread, consider using
-// base::Create(Sequenced|SingleTreaded)TaskRunnerWithTraits().
+// base::Create(Sequenced|SingleThread)TaskRunnerWithTraits().
 //
 // A simple thread abstraction that establishes a MessageLoop on a new thread.
 // The consumer uses the MessageLoop of the thread to cause code to execute on