move checkLE functionality directly onto readbuffer

Bug: skia:
Change-Id: I549717f04e2e4cafc41ccbe13009805f47943d5d
Reviewed-on: https://skia-review.googlesource.com/99703
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
12 files changed