Fix issue with aspect ratio not applying correctly when PIP is expanded

- The current code always used the default min edge size to calculate the
  PIP bounds when the aspect ratio changes, so if a PIP app sets the aspect
  ratio in response to the an action, the bounds would be resized down
  incorrectly.
- This CL fixes the issue with current aspect ratio not being initialized
  correctly, and also ensures that SystemUI always updates the min edge
  size when expanding the PIP.

Bug: 38324839
Test: android.server.cts.ActivityManagerPinnedStackTests
Test: go/wm-smoke

Change-Id: Ida0f68b2f8f93f9bf1915dda8762a156704d4709
diff --git a/services/core/java/com/android/server/am/PinnedActivityStack.java b/services/core/java/com/android/server/am/PinnedActivityStack.java
index 702bf92..2010c24 100644
--- a/services/core/java/com/android/server/am/PinnedActivityStack.java
+++ b/services/core/java/com/android/server/am/PinnedActivityStack.java
@@ -44,9 +44,9 @@
         return new PinnedStackWindowController(mStackId, this, displayId, onTop, outBounds);
     }
 
-    Rect getPictureInPictureBounds(float aspectRatio, boolean useExistingStackBounds) {
+    Rect getDefaultPictureInPictureBounds(float aspectRatio) {
         return getWindowContainerController().getPictureInPictureBounds(aspectRatio,
-                useExistingStackBounds);
+                null /* currentStackBounds */);
     }
 
     void animateResizePinnedStack(Rect sourceHintBounds, Rect toBounds, int animationDuration,