Specify CPU (buffer) and GPU (shader) types explicitly in Attribute

The CPU type is still specified using GrVertexAttribType.
The GPU type is specified directly using GrSLType.

kHalfX_GrVertexAttribType now really means half-float buffer
data, rather than float. (Caveat: The GL enum is only correct
with ES3/GL3 - ES2+extension needs a different value. Sigh.)

Bug: skia:
Change-Id: Ife101db68a5d4ea1ddc2f6c60fbec0c66d725c16
Reviewed-on: https://skia-review.googlesource.com/154628
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
28 files changed