Use ScopedTaskEnvironment instead of MessageLoop

MessageLoop will go away, eventually.

ScopedTaskEnvironment will per default start a ThreadPool, which should
be fine in most of the cases. If you belive your test needs to make sure
that no ThreadPool runs let me know and I will update the patch.

BUG=891670
This CL was uploaded by git cl split.

R=liberato@chromium.org

Change-Id: Ie344bc13910dac814dc6ba8ecf8f0d7e63075540
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635822
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664786}

media/gpu/android/surface_texture_gl_owner_unittest.cc

@@ -10,7 +10,7 @@
 
 #include "base/bind.h"
 #include "base/logging.h"
-#include "base/message_loop/message_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "media/gpu/android/mock_abstract_texture.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -74,7 +74,7 @@ class SurfaceTextureGLOwnerTest : public testing::Test {
   scoped_refptr<gl::GLContext> context_;
   scoped_refptr<gl::GLShareGroup> share_group_;
   scoped_refptr<gl::GLSurface> surface_;
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 };
 
 TEST_F(SurfaceTextureGLOwnerTest, OwnerReturnsServiceId) {