Refactoring design-mode-spellcheck-off.html to use asynchronous spellchecking
https://bugs.webkit.org/show_bug.cgi?id=127770

Reviewed by Ryosuke Niwa.

Enable asynchronous spellchecking in design-mode-spellcheck-off.html.

Due to js-test-pre.js adds some HTML elements inside the BODY, the misspelled
phrase was moved into separated div element. It allows to check spelling marker
on desired element instead of whole body.

It turned out that the test does not underline "asdf" as misspelled although
spellcheck attribute is on. To force spellchecking, the caret needs to be moved
out of the misspelled word. To be more reliable, the test now contains two test
cases in 'desingMode=on' when spellcheck attribute is off and on.

* editing/spelling/design-mode-spellcheck-off-expected.txt:
* editing/spelling/design-mode-spellcheck-off.html:

* platform/gtk-wk2/TestExpectations:
* platform/gtk/TestExpectations:
Skip the test for GTK.

* platform/win/TestExpectations:
Add failing test expectation.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@164101 268f45cc-cd09-0410-ab3c-d52691b4dbfc