Animate alpha for bubbles and background (3/n)

Use separate timings for bubble icons and bubble bar background when
stashing and unstashing.
Follows alpha timings applied to taskbar background and icons.

Bug: 345488489
Test: TransientBubbleStashControllerTest
Test: stash and unstash bubble bar in app by swiping up from taskbar
Test: expand and collapse bubble bar in app by swiping up on bar
Test: expand and collapse bubble bar on home screen by tapping on it
Flag: com.android.wm.shell.enable_bubble_bar
Change-Id: I485f6346539cb6c8ea6dd4d15f25a6421021fec1

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

@@ -86,6 +86,9 @@ public class BubbleBarViewController {
 
     // These are exposed to {@link BubbleStashController} to animate for stashing/un-stashing
     private final MultiValueAlpha mBubbleBarAlpha;
+    private final AnimatedFloat mBubbleBarBubbleAlpha = new AnimatedFloat(this::updateBubbleAlpha);
+    private final AnimatedFloat mBubbleBarBackgroundAlpha = new AnimatedFloat(
+            this::updateBackgroundAlpha);
     private final AnimatedFloat mBubbleBarScaleX = new AnimatedFloat(this::updateScaleX);
     private final AnimatedFloat mBubbleBarScaleY = new AnimatedFloat(this::updateScaleY);
     private final AnimatedFloat mBubbleBarBackgroundScaleX = new AnimatedFloat(
@@ -268,6 +271,14 @@ public class BubbleBarViewController {
         return mBubbleBarAlpha;
     }
 
+    public AnimatedFloat getBubbleBarBubbleAlpha() {
+        return mBubbleBarBubbleAlpha;
+    }
+
+    public AnimatedFloat getBubbleBarBackgroundAlpha() {
+        return mBubbleBarBackgroundAlpha;
+    }
+
     public AnimatedFloat getBubbleBarScaleX() {
         return mBubbleBarScaleX;
     }
@@ -561,6 +572,14 @@ public class BubbleBarViewController {
         mBarView.setBackgroundScaleY(scale);
     }
 
+    private void updateBubbleAlpha(float alpha) {
+        mBarView.setBubbleAlpha(alpha);
+    }
+
+    private void updateBackgroundAlpha(float alpha) {
+        mBarView.setBackgroundAlpha(alpha);
+    }
+
     //
     // Manipulating the specific bubble views in the bar
     //