Add UseCounters for lang and xml:lang content attributes.

We'd like to investigation how many pages will be affected by the feature [1].
This CL also adds counters for <input type=submit>, which is a typical
affected element.

[1] https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/QpEoCwU0Ttg

BUG=141169

Review URL: https://codereview.chromium.org/706503002

git-svn-id: svn://svn.chromium.org/blink/trunk@184882 bbb929c8-8fbe-4397-9dbb-9b2b20218538