Provide a CSSParserContext to CSSSyntaxDescriptor

Add a CSSParserContext* argument to CSSSyntaxDescriptor::parse to allow
CSSValues to be resolve against a proper parser context, and resolve
relative URLs and other sourcing sensitive data.
Provide parser contexts as available on call-sites, or use the
strictCSSParserContext() if none is available. Move the TODO up the
callstack as needed.

BUG=618165

Review-Url: https://codereview.chromium.org/2632083002
Cr-Commit-Position: refs/heads/master@{#443882}
5 files changed