Clean up keyword only property case

Some clean ups related to the parser case where a property only supports keywords:
- Move 'unicode-bidi' and 'all' to be handled here
- Remove unreachable image-rendering case in parseSVGProperty; this is handled as a keyword only property
- Remove font-stretch case in parseValue; this is handled as a keyword only property
- Remove duplicate listing of keyword only properties in parseValue. This doesn't seem to add anything except more places to change in the keyword only case.

BUG=404023

Review URL: https://codereview.chromium.org/481273004

git-svn-id: svn://svn.chromium.org/blink/trunk@180752 bbb929c8-8fbe-4397-9dbb-9b2b20218538