XMLHttpRequest.responseURL should exclude url
fragment

According to the specification of responseURL, it will return empty string
if the response URL is null otherwise it will return its serialization with exclude fragment flag set.

Specs : https://xhr.spec.whatwg.org/#the-responseurl-attribute

To check this added test for URL like "/xmlhttprequest/navigation-target.html#foobar"
in responseURL.html test, according to specs for this case responseURL attribute will return url excluding fragments.

So removing fragments from response URL in responseURL() method.
R=habib.virji@samsung.com
BUG=427789

Review URL: https://codereview.chromium.org/681513003

git-svn-id: svn://svn.chromium.org/blink/trunk@184513 bbb929c8-8fbe-4397-9dbb-9b2b20218538