eliminated GrGLSLExpr

Now that skslc performs all of the optimizations (and then some) that
GrGLSLExpr is responsible for, it's just extra work for no benefit.

Bug: skia:
Change-Id: I40b0629e00a33873ed9fc6c0a9f41d8350221f9a
Reviewed-on: https://skia-review.googlesource.com/14560
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
31 files changed