applist: Fix two flaky HomeScreenControllerTest tests.

Ran locally and seems fixed. I think the cause was base::RunLOops which
used to be needed for changing tablet mode, but thats no longer the case
so they just messed up some other waits.

Bug: 1027899, 1027800
Change-Id: Icf6cfd70e0e2ef826a3767a20a7bca75f31aacd8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1947165Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Commit-Queue: Sammie Quon <sammiequon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721230}

ash/home_screen/home_screen_controller_unittest.cc

@@ -105,9 +105,7 @@ TEST_P(HomeScreenControllerTest, ShowLauncherHistograms) {
   ui::ScopedAnimationDurationScaleMode test_duration_mode(
       ui::ScopedAnimationDurationScaleMode::NON_ZERO_DURATION);
 
-  base::RunLoop().RunUntilIdle();
   Shell::Get()->tablet_mode_controller()->SetEnabledForTest(true);
-  base::RunLoop().RunUntilIdle();
 
   auto window = CreateTestWindow();
   base::HistogramTester tester;
@@ -130,9 +128,7 @@ TEST_P(HomeScreenControllerTest, DraggingHistograms) {
   ui::ScopedAnimationDurationScaleMode test_duration_mode(
       ui::ScopedAnimationDurationScaleMode::NON_ZERO_DURATION);
 
-  base::RunLoop().RunUntilIdle();
   Shell::Get()->tablet_mode_controller()->SetEnabledForTest(true);
-  base::RunLoop().RunUntilIdle();
 
   base::HistogramTester tester;
   tester.ExpectTotalCount(kHomescreenAnimationHistogram, 0);