URLPattern: Support constructor strings with ipv6 addresses.

This adds support for constructor strings like:

  new URLPattern("http://[\\:\\:1]/");

As discussed in spec issue #113:

  whatwg/urlpattern#113

Fixed: 1245760
Change-Id: I712341e72a5c2af745dbbdbb8673a79809a98425
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3138336
Commit-Queue: Ben Kelly <wanderview@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/main@{#917682}

urlpattern/resources/urlpatterntestdata.json

@@ -2150,6 +2150,55 @@
       "pathname": { "input": "/data:channel.html", "groups": {} }
     }
   },
+  {
+    "pattern": [ "http://[\\:\\:1]/" ],
+    "inputs": [ "http://[::1]/" ],
+    "exactly_empty_components": [ "username", "password", "port", "search",
+                                  "hash" ],
+    "expected_obj": {
+      "protocol": "http",
+      "hostname": "[\\:\\:1]",
+      "pathname": "/"
+    },
+    "expected_match": {
+      "protocol": { "input": "http", "groups": {} },
+      "hostname": { "input": "[::1]", "groups": {} },
+      "pathname": { "input": "/", "groups": {} }
+    }
+  },
+  {
+    "pattern": [ "http://[\\:\\:1]:8080/" ],
+    "inputs": [ "http://[::1]:8080/" ],
+    "exactly_empty_components": [ "username", "password", "search", "hash" ],
+    "expected_obj": {
+      "protocol": "http",
+      "hostname": "[\\:\\:1]",
+      "port": "8080",
+      "pathname": "/"
+    },
+    "expected_match": {
+      "protocol": { "input": "http", "groups": {} },
+      "hostname": { "input": "[::1]", "groups": {} },
+      "port": { "input": "8080", "groups": {} },
+      "pathname": { "input": "/", "groups": {} }
+    }
+  },
+  {
+    "pattern": [ "http://[\\:\\:a]/" ],
+    "inputs": [ "http://[::a]/" ],
+    "exactly_empty_components": [ "username", "password", "port", "search",
+                                  "hash" ],
+    "expected_obj": {
+      "protocol": "http",
+      "hostname": "[\\:\\:a]",
+      "pathname": "/"
+    },
+    "expected_match": {
+      "protocol": { "input": "http", "groups": {} },
+      "hostname": { "input": "[::a]", "groups": {} },
+      "pathname": { "input": "/", "groups": {} }
+    }
+  },
   {
     "pattern": [ "https://foo{{@}}example.com" ],
     "inputs": [ "https://foo@example.com" ],