Backport some tests in...

Backport some tests in /content/browser/renderer_host/embedded_frame_sink_provider_impl_unittest.cc to SingleThreadTaskEnvironment

These tests were previously migrated from single-threaded MessageLoop to
a multi-threaded TaskEnvironment (then named ScopedTaskEnvironment) as
part of crbug.com/891670.

//base OWNERS decided in retrospect that it was better to keep a
single-threaded option for TaskEnvironment and introduced
SingleThreadTaskEnvironment. This CL retrofits that decision for
/content/browser/renderer_host/embedded_frame_sink_provider_impl_unittest.cc.

This CL is a no-op if it passes CQ.

This CL was uploaded by git cl split.

R=kylechar@chromium.org

Bug: 891670
Change-Id: I31b489442139463f8f7a80705381c71bbf95da52
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1786805
Auto-Submit: Gabriel Charette <gab@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693692}

content/browser/renderer_host/embedded_frame_sink_provider_impl_unittest.cc

@@ -154,7 +154,7 @@ class EmbeddedFrameSinkProviderImplTest : public testing::Test {
  private:
   // A MessageLoop is required for mojo bindings which are used to
   // connect to graphics services.
-  base::test::TaskEnvironment task_environment_;
+  base::test::SingleThreadTaskEnvironment task_environment_;
   viz::ServerSharedBitmapManager shared_bitmap_manager_;
   viz::FakeHostFrameSinkClient host_frame_sink_client_;
   std::unique_ptr<viz::HostFrameSinkManager> host_frame_sink_manager_;