LibWeb: Skip serialization of implicit grid lines created during layout

StyleValues created for grid-template-rows and grid-template-columns by
GFC should not include `-start`/`-end` lines implicitly created by grid
areas.

Libraries/LibWeb/CSS/GridTrackSize.cpp

@@ -166,7 +166,11 @@ String GridLineNames::to_string() const
 {
     StringBuilder builder;
     builder.append("["sv);
-    builder.join(' ', names);
+    for (size_t i = 0; i < m_names.size(); ++i) {
+        if (i > 0)
+            builder.append(" "sv);
+        builder.append(m_names[i].name);
+    }
     builder.append("]"sv);
     return MUST(builder.to_string());
 }
@@ -211,7 +215,8 @@ void GridTrackSizeList::append(GridLineNames&& line_names)
 {
     if (!m_list.is_empty() && m_list.last().has<GridLineNames>()) {
         auto& last_line_names = m_list.last().get<GridLineNames>();
-        last_line_names.names.extend(move(line_names.names));
+        for (auto const& name : line_names.names())
+            last_line_names.append(name.name);
         return;
     }
     m_list.append(move(line_names));

Libraries/LibWeb/CSS/GridTrackSize.h

@@ -78,11 +78,25 @@ private:
     GridSize m_max_grid_size;
 };
 
-struct GridLineNames {
-    Vector<FlyString> names;
+struct GridLineName {
+    FlyString name;
+    bool implicit { false };
+
+    bool operator==(GridLineName const& other) const = default;
+};
+
+class GridLineNames {
+public:
+    void append(FlyString const& name) { m_names.append({ name }); }
+    bool is_empty() const { return m_names.is_empty(); }
+    auto const& names() const& { return m_names; }
 
     String to_string() const;
+
     bool operator==(GridLineNames const& other) const = default;
+
+private:
+    Vector<GridLineName> m_names;
 };
 
 class GridTrackSizeList {

Libraries/LibWeb/CSS/Parser/ValueParsing.cpp

@@ -3291,7 +3291,7 @@ Optional<GridLineNames> Parser::parse_grid_line_names(TokenStream<ComponentValue
         auto maybe_ident = parse_custom_ident(block_tokens, { { "span"sv, "auto"sv } });
         if (!maybe_ident.has_value())
             return OptionalNone {};
-        line_names.names.append(maybe_ident.release_value());
+        line_names.append(maybe_ident.release_value());
         block_tokens.discard_whitespace();
     }
 
@@ -3313,13 +3313,13 @@ size_t Parser::parse_track_list_impl(TokenStream<ComponentValue>& tokens, GridTr
         if (!explicit_grid_track.has_value())
             break;
 
-        if (line_names.has_value() && !line_names->names.is_empty())
+        if (line_names.has_value() && !line_names->is_empty())
             output.append(line_names.release_value());
 
         output.append(explicit_grid_track.release_value());
         if (allow_trailing_line_names_for_each_track == AllowTrailingLineNamesForEachTrack::Yes) {
             auto trailing_line_names = parse_grid_line_names(tokens);
-            if (trailing_line_names.has_value() && !trailing_line_names->names.is_empty()) {
+            if (trailing_line_names.has_value() && !trailing_line_names->is_empty()) {
                 output.append(trailing_line_names.release_value());
             }
         }
@@ -3328,7 +3328,7 @@ size_t Parser::parse_track_list_impl(TokenStream<ComponentValue>& tokens, GridTr
     }
 
     if (allow_trailing_line_names_for_each_track == AllowTrailingLineNamesForEachTrack::No) {
-        if (auto trailing_line_names = parse_grid_line_names(tokens); trailing_line_names.has_value() && !trailing_line_names->names.is_empty()) {
+        if (auto trailing_line_names = parse_grid_line_names(tokens); trailing_line_names.has_value() && !trailing_line_names->is_empty()) {
             output.append(trailing_line_names.release_value());
         }
     }