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

media/capture/video/linux/v4l2_capture_delegate_unittest.cc

Index: media/capture/video/linux/v4l2_capture_delegate_unittest.cc
diff --git a/media/capture/video/linux/v4l2_capture_delegate_unittest.cc b/media/capture/video/linux/v4l2_capture_delegate_unittest.cc
index a22cf59f6e24b7c754fef8ce0c63b070fb0b31f8..d4a77ace1d4829e58211770e386b4747236dbdde 100644
--- a/media/capture/video/linux/v4l2_capture_delegate_unittest.cc
+++ b/media/capture/video/linux/v4l2_capture_delegate_unittest.cc
@@ -7,6 +7,7 @@
 
 #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"
@@ -219,7 +220,7 @@ class V4L2CaptureDelegateTest : public ::testing::Test {
             50)) {}
   ~V4L2CaptureDelegateTest() override = default;
 
-  base::MessageLoop loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   VideoCaptureDeviceDescriptor device_descriptor_;
   std::unique_ptr<V4L2CaptureDelegate> delegate_;
 };