Use ScopedTaskEnvironment instead of MessageLoop in components unit tests.

components/display_compositor/yuv_readback_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 "base/json/json_reader.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/launcher/unit_test_launcher.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_suite.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "components/display_compositor/gl_helper.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
 #include "gpu/command_buffer/client/shared_memory_limits.h"
 #include "gpu/ipc/common/surface_handle.h"
 #include "gpu/ipc/gl_in_process_context.h"
 #include "media/base/video_frame.h"
 #include "media/base/video_util.h"
@@ skipping 449 matching lines @@
         output_frame->stride(media::VideoFrame::kVPlane), 2, output_xsize / 2,
         output_ysize / 2, &input_pixels, message + " V plane");
 
     gl_->DeleteTextures(1, &src_texture);
   }
 
   std::unique_ptr<gpu::GLInProcessContext> context_;
   gpu::gles2::GLES2Interface* gl_;
   std::unique_ptr<display_compositor::GLHelper> helper_;
   gl::DisableNullDrawGLBindings enable_pixel_output_;
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 };
 
 TEST_F(YUVReadbackTest, YUVReadbackOptTest) {
   // This test uses the gpu.service/gpu_decoder tracing events to detect how
   // many scaling passes are actually performed by the YUV readback pipeline.
   StartTracing(TRACE_DISABLED_BY_DEFAULT(
       "gpu.service") "," TRACE_DISABLED_BY_DEFAULT("gpu_decoder"));
 
   TestYUVReadback(800, 400, 800, 400, 0, 0, 1, false, true,
                   display_compositor::GLHelper::SCALER_QUALITY_FAST);
@@ skipping 59 matching lines @@
 INSTANTIATE_TEST_CASE_P(
     ,
     YUVReadbackPixelTest,
     ::testing::Combine(
         ::testing::Bool(),
         ::testing::Bool(),
         ::testing::Range<unsigned int>(0, arraysize(kYUVReadbackSizes)),
         ::testing::Range<unsigned int>(0, arraysize(kYUVReadbackSizes))));
 
 }  // namespace display_compositor