AK: Port URL username/password from DeprecatedString to String

And for cases that just need to check whether the password/username is
empty, add a raw_{password,username} helper to avoid any allocation.

Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp

@@ -42,8 +42,8 @@ static bool url_matches_about_blank(AK::URL const& url)
     // A URL matches about:blank if its scheme is "about", its path contains a single string "blank", its username and password are the empty string, and its host is null.
     return url.scheme() == "about"sv
         && url.serialize_path() == "blank"sv
-        && url.username().is_empty()
-        && url.password().is_empty()
+        && url.raw_username().is_empty()
+        && url.raw_password().is_empty()
         && url.host().has<Empty>();
 }
 

Userland/Libraries/LibWeb/HTML/HTMLHyperlinkElementUtils.cpp

@@ -97,7 +97,7 @@ DeprecatedString HTMLHyperlinkElementUtils::username() const
         return DeprecatedString::empty();
 
     // 3. Return this element's url's username.
-    return m_url->username();
+    return m_url->username().release_value().to_deprecated_string();
 }
 
 // https://html.spec.whatwg.org/multipage/links.html#dom-hyperlink-username
@@ -114,7 +114,7 @@ void HTMLHyperlinkElementUtils::set_username(DeprecatedString username)
         return;
 
     // 4. Set the username given this’s URL and the given value.
-    url->set_username(username);
+    MUST(url->set_username(username));
 
     // 5. Update href.
     update_href();
@@ -134,7 +134,7 @@ DeprecatedString HTMLHyperlinkElementUtils::password() const
         return DeprecatedString::empty();
 
     // 4. Return url's password.
-    return url->password();
+    return url->password().release_value().to_deprecated_string();
 }
 
 // https://html.spec.whatwg.org/multipage/links.html#dom-hyperlink-password
@@ -151,7 +151,7 @@ void HTMLHyperlinkElementUtils::set_password(DeprecatedString password)
         return;
 
     // 4. Set the password, given url and the given value.
-    url->set_password(move(password));
+    MUST(url->set_password(password));
 
     // 5. Update href.
     update_href();

Userland/Libraries/LibWeb/HTML/NavigableContainer.cpp

@@ -215,8 +215,8 @@ static bool url_matches_about_blank(AK::URL const& url)
     // A URL matches about:blank if its scheme is "about", its path contains a single string "blank", its username and password are the empty string, and its host is null.
     return url.scheme() == "about"sv
         && url.serialize_path() == "blank"sv
-        && url.username().is_empty()
-        && url.password().is_empty()
+        && url.raw_username().is_empty()
+        && url.raw_password().is_empty()
         && url.host().has<Empty>();
 }