Add mip support to *DeferredTextureImageData functions.

As a first step, I want to add the ability to store multiple mip levels
in the opaque object.

I will follow this with using SkMipMap to generate and store the mip
levels and generating the texture from those stored mip levels.

R=bsalomon@chromium.org
CC=ericrk@chromium.org
BUG=578304
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2023573002

Review-Url: https://codereview.chromium.org/2023573002
1 file changed