Use generated switch statements instead of hashing to look up HTML tags during innerHTML

This is an 8% performance win on the "tags x 10" portion of
http://jsperf.com/parse-html-type on my Z620.

This is only the first step in introducing switch-based tag lookup to the parser.
In particular, the BackgroundHTMLParser would likely benefit from using this codepath.

BUG=320036

Review URL: https://codereview.chromium.org/76563006

git-svn-id: svn://svn.chromium.org/blink/trunk@162322 bbb929c8-8fbe-4397-9dbb-9b2b20218538