Use echo handler in send-object-tostring-check

It doesn't need to get host echoed back. Just use the simple echo
handler.

Some unnecessary div elements are removed.

BUG=none

Review URL: https://codereview.chromium.org/317113002

git-svn-id: svn://svn.chromium.org/blink/trunk@175633 bbb929c8-8fbe-4397-9dbb-9b2b20218538