Temporarily allow StackView to use a canvas.clipRectUnion

StackView currently expands the clip of the view which is a prohibited
operation in API Level 28.  This CL currently allows this specialized
use case to work in this situation until we can update StackView
to not clip to its bounds and then just intersect with this clip
provided by its parent.

Test: CtsWidgetTestCases
Bug: 77642155
Change-Id: Icc003ad3946bb226368ec2030d4707753f4f55e9