Implement clone() for GrDisplacementEffect

This also adds copy constructors for:
GrTextureDomain
GrFragmentProcessor::TextureSampler
GrCoordTransform
Change-Id: I23cb85113e236f8b6fd1d91163c80d2a41931691
Reviewed-on: https://skia-review.googlesource.com/26621
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed