Start making texture coordinates be absolute

Start making texture coordinates be absolute

The idea here is that we will pass GrTextureProxys in (where we're currently passing GrTextures) and defer the normalization until the texture is actually instantiated (and possibly move it to the GPU entirely)

This CL does (intentionally) change the texturedomaineffect GM but I believe the new behavior is more correct.

Change-Id: I4e0510b3dfb65ff0d0ee5921f9a6f94151e602d3
Reviewed-on: https://skia-review.googlesource.com/6807
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>