Continue making Ganesh use absolute texture coordinates

Continue making Ganesh use absolute texture coordinates

The idea here is that the GrCoordTransform will actually hold a GrTextureProxy (rather than a GrTexture) and then, in GrGLSLPrimitiveProcessor::GetTransformMatrix, use the instantiated width & height (when uploading the transform matrix)

Change-Id: Ibac3a540fcb1967ceef571157d41c1937acfadf8
Reviewed-on: https://skia-review.googlesource.com/6977
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>