LibWeb: Pass values by reference in style value operator== functions

Userland/Libraries/LibWeb/CSS/StyleValue.cpp

@@ -1591,7 +1591,7 @@ String LinearGradientStyleValue::to_string() const
     return builder.to_string();
 }
 
-static bool operator==(LinearGradientStyleValue::GradientDirection a, LinearGradientStyleValue::GradientDirection b)
+static bool operator==(LinearGradientStyleValue::GradientDirection const& a, LinearGradientStyleValue::GradientDirection const& b)
 {
     if (a.has<SideOrCorner>() && b.has<SideOrCorner>())
         return a.get<SideOrCorner>() == b.get<SideOrCorner>();
@@ -1600,22 +1600,22 @@ static bool operator==(LinearGradientStyleValue::GradientDirection a, LinearGrad
     return false;
 }
 
-static bool operator==(GradientColorHint a, GradientColorHint b)
+static bool operator==(GradientColorHint const& a, GradientColorHint const& b)
 {
     return a.value == b.value;
 }
 
-static bool operator==(GradientColorStop a, GradientColorStop b)
+static bool operator==(GradientColorStop const& a, GradientColorStop const& b)
 {
     return a.color == b.color && a.position == b.position && a.second_position == b.second_position;
 }
 
-static bool operator==(ColorStopListElement a, ColorStopListElement b)
+static bool operator==(ColorStopListElement const& a, ColorStopListElement const& b)
 {
     return a.transition_hint == b.transition_hint && a.color_stop == b.color_stop;
 }
 
-static bool operator==(EdgeRect a, EdgeRect b)
+static bool operator==(EdgeRect const& a, EdgeRect const& b)
 {
     return a.top_edge == b.top_edge && a.right_edge == b.right_edge && a.bottom_edge == b.bottom_edge && a.left_edge == b.left_edge;
 }