Add lazy proxy's for wrapping backend textures

Bug: skia:
Change-Id: I3bb557cefc35312adc9515b5683d2ed747bb4eb3
Reviewed-on: https://skia-review.googlesource.com/96862
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
7 files changed