Verify WindowContext gets custom Drawable

Before [1], WindowContext#getDrawable with custom drawable would
lead to app crashes.
This CL adds a test to prevent future regression.

[1]: 09c03ec912419f4e1fe3fbc5980843b4dbd73599

fixes: 203027987
Test: atest WindowContextTest

Change-Id: I46fc81c3e850089b8021053b38e258720023aa68
3 files changed