commit 332293fdcd6ebf1b489304e5d52903ddb2eaf5ea
author alancutter <alancutter@chromium.org> Sat Feb 27 03:31:05 2016
committer Commit bot <commit-bot@chromium.org> Sat Feb 27 03:32:26 2016
tree aabf2465ce999fb9da28a4500e0f10c8ed2b26cf
parent 1ad0be78cd3ea8850ffa9ad3d11560648816cf22

Add additive animation support for CSS property background-size

This patch adds support for composite modes on background-size CSS animations
via element.animate().

This change also makes interpolation between background-size and
-webkit-mask-size fall back to 50% flip behaviour if a keyword is used
to bring us inline with spec text:
https://drafts.csswg.org/css-backgrounds-3/#the-background-size

BUG=437696

Review URL: https://codereview.chromium.org/1689383002

Cr-Commit-Position: refs/heads/master@{#378104}