Align bubble bar stash anim with taskbar (1/n)

Only scale bubble bar background during stash and unstash animation.
Follows the logic used for taskbar. We scale only the background and
clip the icons separately.

Bug: 345488489
Test: PersistentBubbleStashControllerTest
Test: TransientBubbleStashControllerTest
Test: BubbleBarViewAnimatorTest
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: Ifc7922c444f2179fc49643424815e5e7dde519cc

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

@@ -82,6 +82,10 @@ public class BubbleBarViewController {
     private final MultiValueAlpha mBubbleBarAlpha;
     private final AnimatedFloat mBubbleBarScaleX = new AnimatedFloat(this::updateScaleX);
     private final AnimatedFloat mBubbleBarScaleY = new AnimatedFloat(this::updateScaleY);
+    private final AnimatedFloat mBubbleBarBackgroundScaleX = new AnimatedFloat(
+            this::updateBackgroundScaleX);
+    private final AnimatedFloat mBubbleBarBackgroundScaleY = new AnimatedFloat(
+            this::updateBackgroundScaleY);
     private final AnimatedFloat mBubbleBarTranslationY = new AnimatedFloat(
             this::updateTranslationY);
 
@@ -266,6 +270,14 @@ public class BubbleBarViewController {
         return mBubbleBarScaleY;
     }
 
+    public AnimatedFloat getBubbleBarBackgroundScaleX() {
+        return mBubbleBarBackgroundScaleX;
+    }
+
+    public AnimatedFloat getBubbleBarBackgroundScaleY() {
+        return mBubbleBarBackgroundScaleY;
+    }
+
     public AnimatedFloat getBubbleBarTranslationY() {
         return mBubbleBarTranslationY;
     }
@@ -535,6 +547,14 @@ public class BubbleBarViewController {
         mBarView.setScaleY(scale);
     }
 
+    private void updateBackgroundScaleX(float scale) {
+        mBarView.setBackgroundScaleX(scale);
+    }
+
+    private void updateBackgroundScaleY(float scale) {
+        mBarView.setBackgroundScaleY(scale);
+    }
+
     //
     // Manipulating the specific bubble views in the bar
     //