Update spellcheck-attribute.html description

r70512 r72782 added new fields to spellcheck-attribute.html to verify
spellcheck attribute.
Update the test to be more descriptive by dumping additional information
whether the misspelled word should be marked or not.

BUG=n/a

WebKit merge r153932.

Review URL: https://chromiumcodereview.appspot.com/22798003

git-svn-id: svn://svn.chromium.org/blink/trunk@155948 bbb929c8-8fbe-4397-9dbb-9b2b20218538