Add a test case for navigator.isProtocolHandlerRegistered

Add a test case for navigator.isProtocolHandlerRegistered
"navigator.isProtocolHandlerRegistered" throws
the proper exceptions and returns the default state of handler.

TEST=fast/dom/navigatorcontentutils/is-protocol-handler-registered.html
BUG=N/A

Review URL: https://codereview.chromium.org/147083008

git-svn-id: svn://svn.chromium.org/blink/trunk@165944 bbb929c8-8fbe-4397-9dbb-9b2b20218538