Add function to perform color fragment processor elimination while performing FP analysis.

Use this in path and instanced ops.

Change-Id: I6c2d3fc9b3aaa0220c560c70aa1b85515bd35a6d
Reviewed-on: https://skia-review.googlesource.com/10059
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
5 files changed