Custom Elements: Add annotation-xml to reservedNames.
Add a test to validate all reserved names listed in the spec are handled.

BUG=234509

Review URL: https://chromiumcodereview.appspot.com/18835003

git-svn-id: svn://svn.chromium.org/blink/trunk@154351 bbb929c8-8fbe-4397-9dbb-9b2b20218538