Use ScopedTaskEnvironment instead of MessageLoop in media/capture/ unit tests

media/capture/video/linux/v4l2_capture_delegate_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 <sys/fcntl.h>
 #include <sys/ioctl.h>
 
 #include "base/files/file_enumerator.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "media/capture/video/linux/v4l2_capture_delegate.h"
 #include "media/capture/video/video_capture_device.h"
 #include "media/capture/video/video_capture_device_descriptor.h"
 #include "media/capture/video_capture_types.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using ::testing::_;
 
@@ skipping 192 matching lines @@
 class V4L2CaptureDelegateTest : public ::testing::Test {
  public:
   V4L2CaptureDelegateTest()
       : device_descriptor_("Device 0", "/dev/video0"),
         delegate_(base::MakeUnique<V4L2CaptureDelegate>(
             device_descriptor_,
             base::ThreadTaskRunnerHandle::Get(),
             50)) {}
   ~V4L2CaptureDelegateTest() override = default;
 
-  base::MessageLoop loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   VideoCaptureDeviceDescriptor device_descriptor_;
   std::unique_ptr<V4L2CaptureDelegate> delegate_;
 };
 
 }  // anonymous namespace
 
 TEST_F(V4L2CaptureDelegateTest, CreateAndDestroyAndVerifyControls) {
   // Check that there is at least a video device, otherwise bail.
   const base::FilePath path("/dev/");
   base::FileEnumerator enumerator(path, false, base::FileEnumerator::FILES,
@@ skipping 39 matching lines @@
   // their |default_value|s.
   {
     base::ScopedFD device_fd(
         HANDLE_EINTR(open(device_descriptor_.device_id.c_str(), O_RDWR)));
     ASSERT_TRUE(device_fd.is_valid());
     VerifyUserControlsAreSetToDefaultValues(device_fd.get());
   }
 }
 
 };  // namespace media