Fixed the GMM PiP window size

This is a regression caused by ag/9645603 and it happens when the
requested aspect ratio is lesser than 1.

Added additional test cases to PipBoundsHandlerTest

Bug: 146162554
Test: Put GMM into PiP window and comparing the bounds
Test: atest PipBoundsHandlerTest
Change-Id: I356caf79bf122921b1d227d9744a40369feafa6e