Changes URL tests for file path normalization proposal

For whatwg/url#544.

Author: alwinb

url/resources/setters_tests.json

@@ -1672,26 +1672,26 @@
             "href": "file://monkey/",
             "new_value": "\\\\",
             "expected": {
-                "href": "file://monkey/",
-                "pathname": "/"
+                "href": "file://monkey//",
+                "pathname": "//"
             }
         },
         {
             "comment": "File URLs and (back)slashes",
             "href": "file:///unicorn",
             "new_value": "//\\/",
             "expected": {
-                "href": "file:///",
-                "pathname": "/"
+                "href": "file://////",
+                "pathname": "////"
             }
         },
         {
             "comment": "File URLs and (back)slashes",
             "href": "file:///unicorn",
             "new_value": "//monkey/..//",
             "expected": {
-                "href": "file:///",
-                "pathname": "/"
+                "href": "file://///",
+                "pathname": "///"
             }
         },
         {