Revert "Create GrXferProcessor while doing GrProcessorSet analysis."

Revert "Create GrXferProcessor while doing GrProcessorSet analysis."

This reverts commit 0ae0e23696f2ef08503040f8c02765eb58b26ddf.

Reason for revert: static assert failure on ios build

Original change's description:
> Create GrXferProcessor while doing GrProcessorSet analysis.
>
>
> Bug: skia:
> Change-Id: I62a628f9c0536ffb05c8f9d0c9ded5657f93b48e
> Reviewed-on: https://skia-review.googlesource.com/11482
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>
>

TBR=egdaniel@google.com,bsalomon@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: Ifd57367b0326dd2b53c622705a868e246645d589
Reviewed-on: https://skia-review.googlesource.com/12104
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>