Remove some unused GrGLGpu member fields and functions.

-Members related to already removed stencil clear program.
-hasExtension() inline memeber function
-declaration for unimplemented setTextureSwizze() member function.

Change-Id: Ibe6054fcb7f7c8c69cfcbbbb12df95f9dcebf9fe
Reviewed-on: https://skia-review.googlesource.com/c/187305
Commit-Queue: Brian Salomon <bsalomon@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
2 files changed