LibGUI: Make Model::data_matches() take Variant by const-reference

Userland/Applications/Help/ManualModel.cpp

@@ -184,7 +184,7 @@ void ManualModel::update_section_node_on_toggle(const GUI::ModelIndex& index, co
     node->set_open(open);
 }
 
-TriState ManualModel::data_matches(const GUI::ModelIndex& index, GUI::Variant term) const
+TriState ManualModel::data_matches(const GUI::ModelIndex& index, const GUI::Variant& term) const
 {
     auto view_result = page_view(page_path(index));
     if (view_result.is_error() || view_result.value().is_empty())

Userland/Applications/Help/ManualModel.h

@@ -51,7 +51,7 @@ public:
     virtual int row_count(const GUI::ModelIndex& = GUI::ModelIndex()) const override;
     virtual int column_count(const GUI::ModelIndex& = GUI::ModelIndex()) const override;
     virtual GUI::Variant data(const GUI::ModelIndex&, GUI::ModelRole) const override;
-    virtual TriState data_matches(const GUI::ModelIndex&, GUI::Variant) const override;
+    virtual TriState data_matches(const GUI::ModelIndex&, const GUI::Variant&) const override;
     virtual void update() override;
     virtual GUI::ModelIndex parent_index(const GUI::ModelIndex&) const override;
     virtual GUI::ModelIndex index(int row, int column = 0, const GUI::ModelIndex& parent = GUI::ModelIndex()) const override;

Userland/Libraries/LibGUI/Model.h

@@ -74,7 +74,7 @@ public:
     virtual int column_count(const ModelIndex& = ModelIndex()) const = 0;
     virtual String column_name(int) const { return {}; }
     virtual Variant data(const ModelIndex&, ModelRole = ModelRole::Display) const = 0;
-    virtual TriState data_matches(const ModelIndex&, Variant) const { return TriState::Unknown; }
+    virtual TriState data_matches(const ModelIndex&, const Variant&) const { return TriState::Unknown; }
     virtual void update() = 0;
     virtual ModelIndex parent_index(const ModelIndex&) const { return {}; }
     virtual ModelIndex index(int row, int column = 0, const ModelIndex& parent = ModelIndex()) const;