Rename SkConfig8888/SkPixelInfo to SkConvertPixels

BUG=skia:

Change-Id: I4f3c6370b3ef4247aa446716c7c154899925d089
Reviewed-on: https://skia-review.googlesource.com/8442
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
11 files changed