Porting WebKit 114900 to blink: checkLayout() should error out if no data-expected* attributes were found

BUG=233956

Review URL: https://chromiumcodereview.appspot.com/22918026

git-svn-id: svn://svn.chromium.org/blink/trunk@156648 bbb929c8-8fbe-4397-9dbb-9b2b20218538