Update some of the MQ comments, add issue link

Simple updates to the comments refering to issue and spec.

At the same time, fix the style of multiple comments.

Review URL: https://codereview.chromium.org/98763006

git-svn-id: svn://svn.chromium.org/blink/trunk@163177 bbb929c8-8fbe-4397-9dbb-9b2b20218538