Lock down GrQuad ctors, avoid resetting Ws when known to be 1.0

Change-Id: I2df94791af133fcfb3fa491163394369f324bbc3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/256096
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
2 files changed