Add more GURLTest.Resolve examples for clarity.

I was confused about how this worked when writing
http://crrev.com/864993002 and none of the existing
examples clarified it. Is there a utility method that will
just always append to the path? like "a.com/b" and "c"
makes "a.com/b/c"?

Review URL: https://codereview.chromium.org/870413005

Cr-Commit-Position: refs/heads/master@{#313216}
1 file changed