Remove calls to deprecated MessageLoop methods in services.

services/shell/standalone/tracer.cc

Index: services/shell/standalone/tracer.cc
diff --git a/services/shell/standalone/tracer.cc b/services/shell/standalone/tracer.cc
index 2edf844e95bd8d3afeea46cb544533f9e6db2f33..cd6f3bcd0f8752b85a2de0a846ffaab8c30855ab 100644
--- a/services/shell/standalone/tracer.cc
+++ b/services/shell/standalone/tracer.cc
@@ -10,6 +10,7 @@
 #include <utility>
 
 #include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
@@ -42,7 +43,7 @@ void Tracer::Start(const std::string& categories,
         << "Could not parse --trace-startup-duration value "
         << duration_seconds_str;
   }
-  base::MessageLoop::current()->PostDelayedTask(
+  base::MessageLoop::current()->task_runner()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&Tracer::StopAndFlushToFile, base::Unretained(this)),
       base::TimeDelta::FromSeconds(trace_duration_secs));
@@ -94,7 +95,7 @@ void Tracer::StopTracingAndFlushToDisk() {
       // Spin up a new thread to flush things out.
       base::Thread flush_thread("mojo_runner_trace_event_flush");
       flush_thread.Start();
-      flush_thread.message_loop()->PostTask(
+      flush_thread.task_runner()->PostTask(
           FROM_HERE,
           base::Bind(&Tracer::EndTraceAndFlush, base::Unretained(this),
                      trace_filename_,