Delete identity matrix shaders from tessellation

Every shader always has a matrix now. The 4 FMAs (literally) that this
saved by specializing the shader weren't worth it.

Bug: skia:10419
Change-Id: I506dbd6d723f6dd022345956fdb5b60b0dd94932
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/412416
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
7 files changed