url: trim leading slashes of file URL paths

It should trim the slashes after the colon into three for file URL.

PR-URL: #12203
Refs: web-platform-tests/wpt#5195
Fixes: #11188
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

Author: watilde

src/node_url.cc

@@ -1108,12 +1108,14 @@ namespace url {
             state = kFileHost;
           } else {
             if (has_base &&
-                base->scheme == "file:" &&
-                base->flags & URL_FLAGS_HAS_PATH &&
-                base->path.size() > 0 &&
-                NORMALIZED_WINDOWS_DRIVE_LETTER(base->path[0])) {
-              url->flags |= URL_FLAGS_HAS_PATH;
-              url->path.push_back(base->path[0]);
+                base->scheme == "file:") {
+              if (NORMALIZED_WINDOWS_DRIVE_LETTER(base->path[0])) {
+                url->flags |= URL_FLAGS_HAS_PATH;
+                url->path.push_back(base->path[0]);
+              } else {
+                url->flags |= URL_FLAGS_HAS_HOST;
+                url->host = base->host;
+              }
             }
             state = kPath;
             continue;
@@ -1196,6 +1198,14 @@ namespace url {
               url->path.push_back(segment);
             }
             buffer.clear();
+            if (url->scheme == "file:" &&
+                (ch == kEOL ||
+                 ch == '?' ||
+                 ch == '#')) {
+              while (url->path.size() > 1 && url->path[0].length() == 0) {
+                url->path.erase(url->path.begin());
+              }
+            }
             if (ch == '?') {
               url->flags |= URL_FLAGS_HAS_QUERY;
               state = kQuery;

test/fixtures/url-setter-tests.js

@@ -1,7 +1,7 @@
 'use strict';
 
 /* WPT Refs:
-   https://github.com/w3c/web-platform-tests/blob/e48dd15/url/setters_tests.json
+   https://github.com/w3c/web-platform-tests/blob/3eff1bd/url/setters_tests.json
    License: http://www.w3.org/Consortium/Legal/2008/04-testsuite-copyright.html
 */
 module.exports =
@@ -1620,6 +1620,33 @@ module.exports =
                 "href": "sc://example.net/%23",
                 "pathname": "/%23"
             }
+        },
+        {
+            "comment": "File URLs and (back)slashes",
+            "href": "file://monkey/",
+            "new_value": "\\\\",
+            "expected": {
+                "href": "file://monkey/",
+                "pathname": "/"
+            }
+        },
+        {
+            "comment": "File URLs and (back)slashes",
+            "href": "file:///unicorn",
+            "new_value": "//\\/",
+            "expected": {
+                "href": "file:///",
+                "pathname": "/"
+            }
+        },
+        {
+            "comment": "File URLs and (back)slashes",
+            "href": "file:///unicorn",
+            "new_value": "//monkey/..//",
+            "expected": {
+                "href": "file:///",
+                "pathname": "/"
+            }
         }
     ],
     "search": [