Adding uncompressed size function

Missing functionality to be able to reuse portable helpers.

Change-Id: If38e5f2b44cff9fb5f1744a59961ee6902f847f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1876760


Reviewed-by: Sam Maier <smaier@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#709081}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 15d575f97d2de48ad0458732faf11f1a281c94fe