Fix thread misusage in TabGridDialogParentTest (2)

Bug: 997192
Change-Id: I5ddfea43dad58d17007eb6f4f50966d4ac7a29ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1769799
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Reviewed-by: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690164}

chrome/android/features/tab_ui/javatests/src/org/chromium/chrome/browser/tasks/tab_management/TabGridDialogParentTest.java

@@ -118,6 +118,7 @@ public class TabGridDialogParentTest extends DummyUiActivityTestCase {
 
     @Test
     @SmallTest
+    @UiThreadTest
     public void testResetDialog() throws Exception {
         mTabGridDialogContainer.removeAllViews();
         View toolbarView = new View(getActivity());
@@ -339,8 +340,12 @@ public class TabGridDialogParentTest extends DummyUiActivityTestCase {
     public void testDialog_FadeInFadeOut() throws Exception {
         // Setup the the basic fade-in and fade-out animation.
         mTabGridDialogParent.setupDialogAnimation(null);
-        mBackgroundFrameView.setAlpha(1f);
-        mAnimationCardView.setAlpha(1f);
+
+        // Specifically set alpha of animation-related views.
+        TestThreadUtils.runOnUiThreadBlocking(() -> {
+            mBackgroundFrameView.setAlpha(1f);
+            mAnimationCardView.setAlpha(1f);
+        });
 
         // Show the dialog with basic fade-in animation.
         TestThreadUtils.runOnUiThreadBlocking(() -> {