Use ScopedTaskEnvironment instead of MessageLoop in mojo unit tests.

mojo/edk/system/ports/ports_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include <map>
 #include <queue>
 #include <sstream>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/rand_util.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/lock.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread.h"
 #include "mojo/edk/system/ports/event.h"
 #include "mojo/edk/system/ports/node.h"
 #include "mojo/edk/system/ports/node_delegate.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace edk {
 namespace ports {
 namespace test {
@@ skipping 386 matching lines @@
       // NOTE: We only need to support broadcast of events. Events have no
       // payload or ports bytes.
       ScopedMessage new_message(
           new TestMessage(message->num_header_bytes(), 0, 0));
       memcpy(new_message->mutable_header_bytes(), message->header_bytes(),
              message->num_header_bytes());
       node->EnqueueMessage(std::move(new_message));
     }
   }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 
   // Acquired before any operation which makes a Node busy, and before testing
   // if all nodes are idle.
   base::Lock global_lock_;
 
   base::Lock lock_;
   uint64_t next_port_id_ = 1;
   std::map<NodeName, TestNode*> nodes_;
 };
 
@@ skipping 1028 matching lines @@
 
   // Expect everything to have gone away.
   EXPECT_TRUE(node0.node().CanShutdownCleanly());
   EXPECT_TRUE(node1.node().CanShutdownCleanly());
 }
 
 }  // namespace test
 }  // namespace ports
 }  // namespace edk
 }  // namespace mojo