Validate source rect hint for enter PIP in gesture nav

If the source rect hint is going outside of visible app bounds,
we should use icon overlay instead.

Test: before http://recall/-/ekEuGtt9d9HWqkUtAzpHx8/fPfOfGUlrBkJ8WbJDqAr2i
Test: after http://recall/-/ekEuGtt9d9HWqkUtAzpHx8/fMcHGqfpA5HCXYoAPV4vTT
Bug: 305090652
Flag: NA

Change-Id: I161f60bf62888c7922227e5d3185810dbe88e317