CSS Tokenizer: Implement <hash-token>

This patch implements <hash-token> from css-syntax. The logic is taken
directly from http://dev.w3.org/csswg/css-syntax/#consume-token.

BUG=424988

Review URL: https://codereview.chromium.org/661673002

git-svn-id: svn://svn.chromium.org/blink/trunk@184468 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: fix build after r184449.

TBR=oilpan-reviews,haraken
BUG=353932
NOTRY=true

Review URL: https://codereview.chromium.org/681013002

git-svn-id: svn://svn.chromium.org/blink/trunk@184469 bbb929c8-8fbe-4397-9dbb-9b2b20218538