<https://webkit.org/b/119584> [Gtk] URL printing code in DumpRenderTree doesn't match WTR or Mac DRT

Reviewed by Gustavo Noronha Silva.

Following a similar approach as in r153977, return a path string
that is relative to main frame URL or just file name if the
resource is not in the same directory subtree, and replace empty
strings with "(null)".

Source/WebKit/gtk:

Update the AuthenticationCallback used in DumpRenderTree so that
it receives a WebKitWebResource, and update
dispatchDidReceiveAuthenticationChallenge so that it retrieves the
WebKitWebResource and passes it to the callback.

* WebCoreSupport/DumpRenderTreeSupportGtk.h: Update the
AuthenticationCallback adding a WebKitWebResource parameter.
* WebCoreSupport/FrameLoaderClientGtk.cpp:
(WebKit::toString): Define this function earlier so we can use it
to get the WebKitWebResource from the identifier in the
AuthenticationChallenge.
(WebKit::FrameLoaderClient::dispatchDidReceiveAuthenticationChallenge):
Use toString to retrieve a WebKitWebResource from the identifier
in the authentication challenge, and pass that WebKitWebResource
to the AuthenticationCallback.

Tools:

Update pathFromSoupURI so it behaves more closely to the other
ports, and remove the unused code after we no longer print
<unknown> in certain cases. Also move
soupURIToStringPreservingPassword to DumpRenderTreeGtk so it can
be used both in TestRunnerGtk and in DumpRenderTree.

* DumpRenderTree/gtk/DumpRenderTree.cpp:
(soupURIToStringPreservingPassword): Moved from TestRunnerGtk so
we can print Soup URIs with the password, since soup_uri_to_string
doesn't preserve them.
(pathFromSoupURI): Updated following EFL implementation in
r153977, and return a WTFString instead of a CString.
(convertSoupMessageToURLPath): Return "(null)" instead of empty
strings, and handle the new return type of pathFromSoupURI.
(convertWebResourceToURLPath): Use a GOwnPtr to hold the Soup URI
reference, and handle the new return type of pathFromSoupURI.
(descriptionSuitableForTestResult): Remove unused code.
(didFinishLoading): Use convertResourceToURLPath.
(didFailLoadingWithError): Use convertResourceToURLPath.
(authenticationCallback): Display the URL of the authentication
challenge.
* DumpRenderTree/gtk/DumpRenderTreeGtk.h: Declare
soupURIToStringPreservingPassword.
* DumpRenderTree/gtk/TestRunnerGtk.cpp: Remove
soupURIToStringPreservingPassword.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154098 268f45cc-cd09-0410-ab3c-d52691b4dbfc