Add GrFragmentProcessor::clone(), implementation for ColorTableEffect, and unit test.

We occasionally make copies of GrPaints. clone() fill facilitate this case when GrFragmentProcessors are non-shareable.. 

Change-Id: I004e34f6ce8c293f9e0664d26532e44bd6b9fdff
Reviewed-on: https://skia-review.googlesource.com/26360
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
5 files changed