[Web Payment][Android] No animation of null bottom sheet.

Before this patch, skip-the-sheet flow on Android would attempt to
animate out the browser sheet when showing transaction errors, even
though the sheet was not shown.

This patch checks for presence of the sheet before animating it.

After this patch, the browser checks for existence of the sheet before
animating it out.

Bug: 952283
Change-Id: I7e7179edce53f10d8d156159192a31e2cc2d5795
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1818223
Commit-Queue: Rouslan Solomakhin <rouslan@chromium.org>
Reviewed-by: Danyao Wang <danyao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699374}

chrome/android/java/src/org/chromium/chrome/browser/payments/ui/DimmingDialog.java

@@ -31,6 +31,9 @@ import org.chromium.chrome.browser.ui.widget.animation.AnimatorProperties;
 import org.chromium.chrome.browser.ui.widget.animation.Interpolators;
 import org.chromium.chrome.browser.util.ColorUtils;
 
+import java.util.ArrayList;
+import java.util.Collection;
+
 /**
  * A fullscreen semitransparent dialog used for dimming Chrome when overlaying a bottom sheet
  * dialog/CCT or an alert dialog on top of it. FLAG_DIM_BEHIND is not being used because it causes
@@ -196,25 +199,31 @@ import org.chromium.chrome.browser.util.ColorUtils;
         public DisappearingAnimator(boolean removeDialog) {
             mIsDialogClosing = removeDialog;
 
-            View child = mFullContainer.getChildAt(0);
-            assert child != null;
+            Collection<Animator> animators = new ArrayList<>();
 
-            Animator sheetFader = ObjectAnimator.ofFloat(child, View.ALPHA, child.getAlpha(), 0f);
-            Animator sheetTranslator =
-                    ObjectAnimator.ofFloat(child, View.TRANSLATION_Y, 0f, mAnimatorTranslation);
+            View child = mFullContainer.getChildAt(0);
+            if (child != null) {
+                // Sheet fader.
+                animators.add(ObjectAnimator.ofFloat(child, View.ALPHA, child.getAlpha(), 0f));
+                // Sheet translator.
+                animators.add(ObjectAnimator.ofFloat(
+                        child, View.TRANSLATION_Y, 0f, mAnimatorTranslation));
+            }
 
-            AnimatorSet current = new AnimatorSet();
-            current.setDuration(DIALOG_EXIT_ANIMATION_MS);
-            current.setInterpolator(Interpolators.FAST_OUT_LINEAR_IN_INTERPOLATOR);
             if (mIsDialogClosing) {
-                Animator scrimFader = ObjectAnimator.ofInt(mFullContainer.getBackground(),
-                        AnimatorProperties.DRAWABLE_ALPHA_PROPERTY, 127, 0);
-                current.playTogether(sheetFader, sheetTranslator, scrimFader);
-            } else {
-                current.playTogether(sheetFader, sheetTranslator);
+                // Scrim fader.
+                animators.add(ObjectAnimator.ofInt(mFullContainer.getBackground(),
+                        AnimatorProperties.DRAWABLE_ALPHA_PROPERTY, 127, 0));
             }
 
+            if (animators.isEmpty()) return;
+
             mIsAnimatingDisappearance = true;
+
+            AnimatorSet current = new AnimatorSet();
+            current.setDuration(DIALOG_EXIT_ANIMATION_MS);
+            current.setInterpolator(Interpolators.FAST_OUT_LINEAR_IN_INTERPOLATOR);
+            current.playTogether(animators);
             current.addListener(this);
             current.start();
         }