AK+Tests+LibWeb: Make `URL::complete_url()` take a StringView

All it does is pass this to `URLParser::parse()` which takes a
StringView, so we might as well take one here too.

AK/URL.cpp

@@ -39,12 +39,12 @@ DeprecatedString URL::path() const
     return builder.to_deprecated_string();
 }
 
-URL URL::complete_url(DeprecatedString const& string) const
+URL URL::complete_url(StringView relative_url) const
 {
     if (!is_valid())
         return {};
 
-    return URLParser::parse(string, this);
+    return URLParser::parse(relative_url, this);
 }
 
 void URL::set_scheme(DeprecatedString scheme)

AK/URL.h

@@ -88,7 +88,7 @@ public:
 
     bool equals(URL const& other, ExcludeFragment = ExcludeFragment::No) const;
 
-    URL complete_url(DeprecatedString const&) const;
+    URL complete_url(StringView) const;
 
     bool data_payload_is_base64() const { return m_data_payload_is_base64; }
     DeprecatedString const& data_mime_type() const { return m_data_mime_type; }

Tests/AK/TestURL.cpp

@@ -403,7 +403,7 @@ TEST_CASE(complete_file_url_with_base)
     EXPECT_EQ(url.paths()[0], "home");
     EXPECT_EQ(url.paths()[1], "index.html");
 
-    auto sub_url = url.complete_url("js/app.js");
+    auto sub_url = url.complete_url("js/app.js"sv);
     EXPECT(sub_url.is_valid());
     EXPECT_EQ(sub_url.path(), "/home/js/app.js");
 }

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -77,9 +77,9 @@ bool ParsingContext::in_quirks_mode() const
 }
 
 // https://www.w3.org/TR/css-values-4/#relative-urls
-AK::URL ParsingContext::complete_url(DeprecatedString const& addr) const
+AK::URL ParsingContext::complete_url(StringView relative_url) const
 {
-    return m_url.complete_url(addr);
+    return m_url.complete_url(relative_url);
 }
 
 Parser::Parser(ParsingContext const& context, StringView input, StringView encoding)

Userland/Libraries/LibWeb/CSS/Parser/Parser.h

@@ -43,7 +43,7 @@ public:
 
     bool in_quirks_mode() const;
     DOM::Document const* document() const { return m_document; }
-    AK::URL complete_url(DeprecatedString const&) const;
+    AK::URL complete_url(StringView) const;
 
     PropertyID current_property_id() const { return m_current_property_id; }
     void set_current_property_id(PropertyID property_id) { m_current_property_id = property_id; }