Fix *Fail* tests in unregisterProtocolHandler test

In fast/dom/unregister-protocol-handler.html, some test field related to check an invalid url has been failed
because wrong syntax error string(SYNTAX_ERR) is used so far. This cl fix it with *SyntaxError*.

Additionally this cl improve error logs of unregister-protocol-handler.html.

BUG=N/A
TEST=LayoutTests/fast/dom/unregister-protocol-handler.html

Review URL: https://codereview.chromium.org/130823002

git-svn-id: svn://svn.chromium.org/blink/trunk@164827 bbb929c8-8fbe-4397-9dbb-9b2b20218538