MessageLoop: wire the unused static method in base::Thread (follow-up cleanup)

base/threading/thread.cc

Index: base/threading/thread.cc
diff --git a/base/threading/thread.cc b/base/threading/thread.cc
index 6ca1caea099d344fa5c44cebd7310bd5c7078777..7bff24232e2bf2d66fda4485a4246ebae2e98332 100644
--- a/base/threading/thread.cc
+++ b/base/threading/thread.cc
@@ -94,8 +94,9 @@ bool Thread::StartWithOptions(const Options& options) {
     type = MessageLoop::TYPE_CUSTOM;
 
   message_loop_timer_slack_ = options.timer_slack;
-  message_loop_ = new MessageLoop(type, options.message_pump_factory);
-
+  scoped_ptr<MessageLoop> message_loop = MessageLoop::CreateUnbound(
+      type, options.message_pump_factory);
+  message_loop_ = message_loop.get();
   start_event_.reset(new WaitableEvent(false, false));
 
   // Hold the thread_lock_ while starting a new thread, so that we can make sure
@@ -111,13 +112,16 @@ bool Thread::StartWithOptions(const Options& options) {
     }
     if (!created) {
       DLOG(ERROR) << "failed to create thread";
-      delete message_loop_;
       message_loop_ = nullptr;
       start_event_.reset();
       return false;
     }
   }
 
+  // The ownership of message_loop is managemed by the newly created thread
+  // within the ThreadMain.
+  ignore_result(message_loop.release());
+
   DCHECK(message_loop_);
   return true;
 }