Reland "Respect canvas size and frame offset in webp decoder"

Original Change Reviewed At:
https://skia-review.googlesource.com/c/7800

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-MSAN

BUG=skia:6185

Change-Id: I92baa9070e15ef3c62dd347c08c906c2715dda10
Reviewed-on: https://skia-review.googlesource.com/8050
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
5 files changed