Add support for internal gl format in GrGLTextureInfo

This gives clients the ability to wrap GL textures with just the GL Format.
This enables us to distinquish between wrapping in Alpha8 texture that is
implented with Alpha or Red format

Bug: skia:
Change-Id: Iacbea60a149c436c270b7ff9ce5d019947678793
Reviewed-on: https://skia-review.googlesource.com/72600
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
7 files changed