AK: Fix IPv6 serialization on multiple '0' parts ending in a '0' part

This could happen if a sequence of '0' parts was followed by a longer
sequence of '0' parts at the end of the host. The first sequence was
being used for the compress, and not the second.

For example, [1:1:0:0:1:0:0:0] was being serialized as: [1:1::1:0:0:0]
instead of [1:1:0:0:1::].

Fix this by checking at the end of the loop if we are in the middle of a
sequence of '0' parts that is longer than the current longest.

AK/URLParser.cpp

@@ -250,6 +250,11 @@ static void serialize_ipv6_address(URL::IPv6Address const& address, StringBuilde
         }
     }
 
+    if (current_sequence_length > longest_sequence_length) {
+        longest_sequence_length = current_sequence_length;
+        compress = current_sequence_start;
+    }
+
     // 3. If there is no sequence of address’s IPv6 pieces that are 0 that is longer than 1, then set compress to null.
     if (longest_sequence_length <= 1)
         compress = {};

Tests/LibWeb/Text/expected/URL/url.txt

@@ -25,3 +25,12 @@ hostname => '[1:0:1:0:1:0:1:0]'
 port => ''
 pathname => '/'
 search => ''
+http://[1:1:0:0:1:0:0:0]/
+protocol => 'http:'
+username => ''
+password => ''
+host => '[1:1:0:0:1::]'
+hostname => '[1:1:0:0:1::]'
+port => ''
+pathname => '/'
+search => ''

Tests/LibWeb/Text/input/URL/url.html

@@ -18,6 +18,7 @@
             'ftp://serenityos.org:21',
             'http://[0:1:0:1:0:1:0:1]',
             'http://[1:0:1:0:1:0:1:0]',
+            'http://[1:1:0:0:1:0:0:0]/',
         ]) {
             printURL(url);
         }