CSP 1.1: Apply hashes to style elements.

Currently we allow hashes only in 'script-src' directives. This patch
adds support for whitelisting hashed inline styles via 'style-src'.

BUG=335489
NOTRY=true

Review URL: https://codereview.chromium.org/138033019

git-svn-id: svn://svn.chromium.org/blink/trunk@165392 bbb929c8-8fbe-4397-9dbb-9b2b20218538