Remove calls to deprecated MessageLoop methods in sync.

sync/internal_api/public/base/cancelation_signal_unittest.cc

Index: sync/internal_api/public/base/cancelation_signal_unittest.cc
diff --git a/sync/internal_api/public/base/cancelation_signal_unittest.cc b/sync/internal_api/public/base/cancelation_signal_unittest.cc
index e367015dd8f4f07dcc23230f6b8abf29dbb041bc..dbd19eb8c6299be2eaec733a0d9a12767f87fc15 100644
--- a/sync/internal_api/public/base/cancelation_signal_unittest.cc
+++ b/sync/internal_api/public/base/cancelation_signal_unittest.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread.h"
@@ -63,12 +64,10 @@ BlockingTask::~BlockingTask() {
 void BlockingTask::RunAsync(base::WaitableEvent* task_start_signal,
                             base::WaitableEvent* task_done_signal) {
   exec_thread_.Start();
-  exec_thread_.message_loop()->PostTask(
-      FROM_HERE,
-      base::Bind(&BlockingTask::Run,
-                 base::Unretained(this),
-                 base::Unretained(task_start_signal),
-                 base::Unretained(task_done_signal)));
+  exec_thread_.task_runner()->PostTask(
+      FROM_HERE, base::Bind(&BlockingTask::Run, base::Unretained(this),
+                            base::Unretained(task_start_signal),
+                            base::Unretained(task_done_signal)));
 }
 
 void BlockingTask::Run(