We want to cover all of zlib's external APIs.
deflateSetDictionary() currently isn't covered.

BUG=780926

Change-Id: Ie2da648a4d58fca0745c814b004d3859e81a85a6
Reviewed-on: https://chromium-review.googlesource.com/752070


Reviewed-by: Max Moroz <mmoroz@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Commit-Queue: Chris Blume <cblume@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#513917}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 425d4cd82b3cdee276acf851d46d3eaf7662946a