Clear corner radius of pip task when changing to fullscreen

Otherwise if only window crop is cleared, the radius crop may be
invalid and cause to show blank content (since commit 9dbf8e8).

Bug: 202923832
Test: Expand PiP from portrait display to fullscreen landscape
Change-Id: I8cbee157167d52ebd9fc0606f23d8d8e0cbc70d7

services/core/java/com/android/server/wm/Task.java

@@ -1926,6 +1926,7 @@ class Task extends TaskFragment {
             final ActivityRecord r = topRunningActivity();
             if (r != null && mDisplayContent.isFixedRotationLaunchingApp(r)) {
                 getSyncTransaction().setWindowCrop(mSurfaceControl, null)
+                        .setCornerRadius(mSurfaceControl, 0f)
                         .setMatrix(mSurfaceControl, Matrix.IDENTITY_MATRIX, new float[9]);
             }
         }