Polish back-to-home animation for 3-button-nav

Move window to the screen center when the animation is driven by a long press on the back button in 3-button-nav.

Bug: 373544911
Test: Manual, i.e. verify that app is center scaled
Flag: com.android.window.flags.predictive_back_three_button_nav
Change-Id: I8bacb923e3c81d99ddc1a8900bcc7423c8276c55
diff --git a/quickstep/src/com/android/quickstep/LauncherBackAnimationController.java b/quickstep/src/com/android/quickstep/LauncherBackAnimationController.java
index 6719ab7..1418671 100644
--- a/quickstep/src/com/android/quickstep/LauncherBackAnimationController.java
+++ b/quickstep/src/com/android/quickstep/LauncherBackAnimationController.java
@@ -384,10 +384,11 @@
         // Move the window along the Y axis.
         float top = (screenHeight - height) * 0.5f + deltaY;
         // Move the window along the X axis.
-        float left = event.getSwipeEdge() == BackEvent.EDGE_RIGHT
-                ? progress * mWindowScaleMarginX
-                : screenWidth - progress * mWindowScaleMarginX - width;
-
+        float left = switch (event.getSwipeEdge()) {
+            case BackEvent.EDGE_RIGHT -> progress * mWindowScaleMarginX;
+            case BackEvent.EDGE_LEFT -> screenWidth - progress * mWindowScaleMarginX - width;
+            default -> (screenWidth - width) / 2;
+        };
         mCurrentRect.set(left, top, left + width, top + height);
         float cornerRadius = Utilities.mapRange(
                 progress, mWindowScaleStartCornerRadius, mWindowScaleEndCornerRadius);