Animate the bubble bar on dismiss

When the last remaining bubble is dismissed by drag or from the menu
we now fade out the bubble bar.

Flag: com.android.wm.shell.enable_bubble_bar
Fixes: 347062801
Test: manual
       - create a single bubble in the bar
       - expand
       - dismiss by drag or from menu
       - observe animation
Change-Id: I86fcaf04c6f5949126744b81e0042b0e58318a13

quickstep/src/com/android/launcher3/taskbar/bubbles/BubbleBarViewController.java

@@ -586,13 +586,17 @@ public class BubbleBarViewController {
     public void setHiddenForBubbles(boolean hidden) {
         if (mHiddenForNoBubbles != hidden) {
             mHiddenForNoBubbles = hidden;
-            updateVisibilityForStateChange();
             if (hidden) {
-                mBarView.setAlpha(0);
-                mBarView.setExpanded(false);
-                adjustTaskbarAndHotseatToBubbleBarState(/* isBubbleBarExpanded = */ false);
+                mBarView.dismiss(() -> {
+                    updateVisibilityForStateChange();
+                    mBarView.setExpanded(false);
+                    adjustTaskbarAndHotseatToBubbleBarState(/* isBubbleBarExpanded= */ false);
+                    mActivity.bubbleBarVisibilityChanged(/* isVisible= */ false);
+                });
+            } else {
+                updateVisibilityForStateChange();
+                mActivity.bubbleBarVisibilityChanged(/* isVisible= */ true);
             }
-            mActivity.bubbleBarVisibilityChanged(!hidden);
         }
     }
 
@@ -625,7 +629,6 @@ public class BubbleBarViewController {
         }
     }
 
-    // TODO: (b/273592694) animate it
     private void updateVisibilityForStateChange() {
         if (!mHiddenForSysui && !mHiddenForNoBubbles && !mHiddenForStashed) {
             mBarView.setVisibility(VISIBLE);