Update tests to account for different pixel snapping behaviors.

With Vulkan HWUI manages the screen rotation directly and when drawn
exactly on pixel boundaries the behavior for snapping pixels in the
x and y axises can be different.  To avoid these differences we update
the tests to draw at pixel centers or use a more fuzzy matching
algorithm.

Test: this
Bug: 205493984
Merged-In: Ic04ed905053aebf97fe9e05f8e32646b747e934c
Change-Id: I8fee75816f5a99f5b73bbd17cc3e3097e18c5787
2 files changed