Replace JPEGCodec::Decode with simple Skia wrapper.

We already use the Skia encoder in this file, so we might as well
use Skia for decoding as well. Using a Skia wrapper here reduces
our attack surface and should win back a bit of code size.

Change-Id: I4a94ba63b71861e746c00c44542cbea11b589307
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5402322


Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1280240}