[css-content] Don't consider a NoneContentData to equal any ContentData

r732549 added a NoneContentData for representing 'content: none'.
But due to a typo, instances of that class were considered to equal any
ContentData instance. That caused problems when changing 'content'
dynamically. This patch fixes the problem.

BUG=1044869

TEST=external/wpt/css/css-content/element-replacement-dynamic.html

Change-Id: If7532d1f859dcaa11b360c02709693b766286fc6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2014910
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Oriol Brufau <obrufau@igalia.com>
Cr-Commit-Position: refs/heads/master@{#734507}
2 files changed