Crop the center when no source rect hint

When there is no source rect hint, forge a crop that matches the given
aspect ratio and centered, therefore we can use a consolidated animation
path and fix the issue with the round corner, which was inproperly
scaled in the past.

Video: http://recall/-/aaaaaabFQoRHlzixHdtY/cfYT91jFXdx5Fd5C1AwOQH
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/c9bvKYnQFaVszr8ouxGkZ6
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/byGhNOhBrN2fVWiSIctxw6
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/hTaRKx1rNQ2WGKqnll0lxI
Flag: NONE bug fix
Bug: 298409662
Test: atest WMShellFlickerTestsPip2:EnterPipViaAppUiButtonTest \
      WMShellFlickerTestsPip2:ExitPipToAppViaIntentTest
Test: Test the overlay in both gesture and button navigation mode,\
      with both YouTube and Google Maps,\
      in both folded and unfolded mode.
Change-Id: Idf191704f6e04d562db8c28d41765da1944c4b68