Add some extra unit-tests to make sure we cover all permutations of {basic_au...

net/http/http_auth_handler_basic_unittest.cc

Index: net/http/http_auth_handler_basic_unittest.cc
===================================================================
--- net/http/http_auth_handler_basic_unittest.cc	(revision 4108)
+++ net/http/http_auth_handler_basic_unittest.cc	(working copy)
@@ -18,6 +18,8 @@
     { L"foo", L"bar", "Basic Zm9vOmJhcg==" },
     // Empty password
     { L"anon", L"", "Basic YW5vbjo=" },
+    // Empty username and empty password.
+    { L"", L"", "Basic Og==" },
   };
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(tests); ++i) {
     std::string challenge = "Basic realm=\"Atlantis\"";