Backport some tests in /ui/events/gesture_detection 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
/ui/events/gesture_detection.

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

This CL was uploaded by git cl split.

R=nzolghadr@chromium.org

Bug: 891670
Change-Id: I3f1e76a565e3cbecb3b5f34e8cb96620fa68df27
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787075
Auto-Submit: Gabriel Charette <gab@chromium.org>
Commit-Queue: Timothy Dresser <tdresser@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695154}

ui/events/gesture_detection/filtered_gesture_provider_unittest.cc

@@ -14,7 +14,8 @@ class FilteredGestureProviderTest : public GestureProviderClient,
                                     public testing::Test {
  public:
   FilteredGestureProviderTest()
-      : task_environment_(base::test::TaskEnvironment::MainThreadType::UI) {}
+      : task_environment_(
+            base::test::SingleThreadTaskEnvironment::MainThreadType::UI) {}
   ~FilteredGestureProviderTest() override {}
 
   // GestureProviderClient implementation.
@@ -22,7 +23,7 @@ class FilteredGestureProviderTest : public GestureProviderClient,
   bool RequiresDoubleTapGestureEvents() const override { return false; }
 
  private:
-  base::test::TaskEnvironment task_environment_;
+  base::test::SingleThreadTaskEnvironment task_environment_;
 };
 
 // Single touch drag test: After touch-start, the moved_beyond_slop_region bit

ui/events/gesture_detection/gesture_provider_unittest.cc

@@ -66,7 +66,8 @@ gfx::RectF BoundsForSingleMockTouchAtLocation(float x, float y) {
 class GestureProviderTest : public testing::Test, public GestureProviderClient {
  public:
   GestureProviderTest()
-      : task_environment_(base::test::TaskEnvironment::MainThreadType::UI) {}
+      : task_environment_(
+            base::test::SingleThreadTaskEnvironment::MainThreadType::UI) {}
   ~GestureProviderTest() override {}
 
   static MockMotionEvent ObtainMotionEvent(base::TimeTicks event_time,
@@ -437,7 +438,7 @@ class GestureProviderTest : public testing::Test, public GestureProviderClient {
   std::vector<GestureEventData> gestures_;
   std::unique_ptr<GestureProvider> gesture_provider_;
   std::unique_ptr<GestureEventData> active_scroll_begin_event_;
-  base::test::TaskEnvironment task_environment_;
+  base::test::SingleThreadTaskEnvironment task_environment_;
   bool should_process_double_tap_events_ = true;
 };