Avoid catastrophic cancellation when computing det for QuadUVMatrix
Avoid catastrophic cancellation when computing det for QuadUVMatrix

With data with large values we can get into situations where clearly
degenerate quads are not giving a zero determinant, because of
errors when computing the additions and subtractions in sequence.
The solution is to compute the subtractions first, and then add them
together.

Bug: oss-fuzz:41445
Change-Id: I7febead4b020e11a137f1703b761af70c14e4e47
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/511796
Reviewed-by: Michael Ludwig <cb1f3dd24de0f0b611b26bc28bec758a551d9b7d@google.com>
Commit-Queue: Jim Van Verth <509afb0bfbb23ecaaf1fb3323209f531b45e75a6@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia