Move background related longhands into CSSPropertyParser

Move the following background related longhands from
LegacyCSSPropertyParser into CSSPropertyParser:

background-blend-mode, background-attachment
background-clip, -webkit-background-clip
-webkit-background-composite, background-image
background-origin, mask-source-type
-webkit-background-origin, background-color
background-position-x, background-position-y
background-size, -webkit-mask-clip
-webkit-mask-composite, Webkit-mask-image
-webkit-mask-origin, -webkit-mask-size
-webkit-mask-position-x, -webkit-mask-position-y
-webkit-mask-repeat-x, -webkit-mask-repeat-y
background-color

BUG=499780

Review URL: https://codereview.chromium.org/1706573002

Cr-Commit-Position: refs/heads/master@{#376677}
7 files changed