Refactoring: Use the given task runner instead of SingleThreadTaskRunnerForTesting

There is no need to use SingleThreadTaskRunnerForTesting here.

Bug: 870606
Change-Id: I2219ece19db82e1636f2cb83eb4570dd1d09b08f
Reviewed-on: https://chromium-review.googlesource.com/1253524Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595724}

media/blink/video_decode_stats_reporter_unittest.cc

@@ -19,7 +19,6 @@
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
-#include "third_party/blink/public/platform/scheduler/test/renderer_scheduler_test_support.h"
 #include "ui/gfx/geometry/rect.h"
 
 using ::testing::Invoke;
@@ -186,8 +185,7 @@ class VideoDecodeStatsReporterTest : public ::testing::Test {
         std::move(recorder_ptr),
         base::Bind(&VideoDecodeStatsReporterTest::GetPipelineStatsCB,
                    base::Unretained(this)),
-        MakeDefaultVideoConfig(),
-        blink::scheduler::GetSingleThreadTaskRunnerForTesting(),
+        MakeDefaultVideoConfig(), task_runner_,
         task_runner_->GetMockTickClock());
   }