[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in cast_channel

MessageLoop will go away, eventually.

BUG=891670

Change-Id: I862c7162f8ce785e3533bb5869050b9047ffd317
Reviewed-on: https://chromium-review.googlesource.com/c/1352753
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611880}

components/cast_channel/cast_transport_unittest.cc

@@ -11,8 +11,8 @@
 #include "base/containers/queue.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/simple_test_clock.h"
 #include "components/cast_channel/cast_framer.h"
 #include "components/cast_channel/cast_socket.h"
@@ -163,7 +163,7 @@ class CastTransportTest : public testing::Test {
     run_loop.RunUntilIdle();
   }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment task_environment_;
   MockCastTransportDelegate* delegate_;
   MockSocket mock_socket_;
   Logger* logger_;

components/cast_channel/keep_alive_delegate_unittest.cc

@@ -9,8 +9,8 @@
 #include "base/json/json_writer.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_mock_time_task_runner.h"
 #include "base/time/tick_clock.h"
 #include "base/timer/mock_timer.h"
@@ -97,7 +97,7 @@ class KeepAliveDelegateTest : public testing::Test {
     run_loop.RunUntilIdle();
   }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment task_environment_;
   MockCastSocket socket_;
   std::unique_ptr<KeepAliveDelegate> keep_alive_;
   scoped_refptr<Logger> logger_;