GitLab

move KeyUsageAllows to the class where its data is. That way the 
function and its contexts is much more understandable. 
This is first part, second part can be found here:
https://crrev.com/1181413009/

Review URL: https://codereview.chromium.org/1184123007

git-svn-id: svn://svn.chromium.org/blink/trunk@201040 bbb929c8-8fbe-4397-9dbb-9b2b20218538