implemented getting format from texture as virtual in gpu caps

Bug: skia:
Change-Id: If6bbbd212ff472ea322d2bbed61995fe7ba85df7
Reviewed-on: https://skia-review.googlesource.com/138240
Commit-Queue: Timothy Liang <timliang@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
14 files changed