Convert two pixel tests, editing/deleting/smart-delete-00{3,4}.html to JS test.

This patch converts two pixel tests, editing/deleting/smart-delete-00{3,4}.html
to JS test, because these tests are no need to be pixel tests.

This patch is a preparation of fixing issue 358947.

BUG=n/a
TEST=no new test because of no behavior changes.

Review URL: https://codereview.chromium.org/428353004

git-svn-id: svn://svn.chromium.org/blink/trunk@179382 bbb929c8-8fbe-4397-9dbb-9b2b20218538