CSP 1.1: Revert CSSOM changes.

In r166627 and r166494, we changed CSP 1.1 to block certain CSSOM
operations if 'unsafe-eval' isn't present in a 'style-src' directive.
This seems to be incompatible with the web; it broke every site using
jQuery, GitHub, etc.

It's not clear that we can (or want to) persue this change; reverting
it for now while we chat about it again in the WG.

BUG=336413,343970

Review URL: https://codereview.chromium.org/169303003

git-svn-id: svn://svn.chromium.org/blink/trunk@167321 bbb929c8-8fbe-4397-9dbb-9b2b20218538