Remove most modifiers of processors on GrPipelineBuilder

Change-Id: I2fc12a97d694e5c0d86c9a4e0818a058905c8cf0
Reviewed-on: https://skia-review.googlesource.com/6993
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
5 files changed