Remove ref keywords

com.unity.shadergraph/Editor/Data/Graphs/BooleanMaterialSlot.cs

         public override SlotValueType valueType { get { return SlotValueType.Boolean; } }
         public override ConcreteSlotValueType concreteValueType { get { return ConcreteSlotValueType.Boolean; } }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Boolean)
             {

com.unity.shadergraph/Editor/Data/Graphs/ColorMaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Color)
             {

com.unity.shadergraph/Editor/Data/Graphs/ColorRGBMaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Color)
             {

com.unity.shadergraph/Editor/Data/Graphs/CubemapInputMaterialSlot.cs

             properties.AddShaderProperty(prop);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Cubemap)
             {

com.unity.shadergraph/Editor/Data/Graphs/DynamicValueMaterialSlot.cs

 			m_ConcreteValueType = valueType;
 		}
 
-		public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+		public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var propType = ConvertConcreteSlotValueTypeToPropertyType(concreteValueType);
 			var pp = new PreviewProperty(propType) { name = name };

com.unity.shadergraph/Editor/Data/Graphs/DynamicVectorMaterialSlot.cs

             m_ConcreteValueType = valueType;
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var propType = ConvertConcreteSlotValueTypeToPropertyType(concreteValueType);
             var pp = new PreviewProperty(propType) { name = name };

com.unity.shadergraph/Editor/Data/Graphs/GradientInputMaterialSlot.cs

             properties.AddShaderProperty(prop);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             properties.Add(new PreviewProperty(PropertyType.Vector1)
             {

com.unity.shadergraph/Editor/Data/Graphs/MaterialSlot.cs

             }
         }
 
-        public virtual void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public virtual void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             properties.Add(default(PreviewProperty));
         }

com.unity.shadergraph/Editor/Data/Graphs/Matrix2MaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Matrix2)
             {

com.unity.shadergraph/Editor/Data/Graphs/Matrix3MaterialSlot.cs

             properties.AddShaderProperty(property);
         }
         
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Matrix3)
             {

com.unity.shadergraph/Editor/Data/Graphs/Matrix4MaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Matrix4)
             {

com.unity.shadergraph/Editor/Data/Graphs/Texture2DInputMaterialSlot.cs

             properties.AddShaderProperty(prop);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Texture)
             {

com.unity.shadergraph/Editor/Data/Graphs/Vector1MaterialSlot.cs

         public override SlotValueType valueType { get { return SlotValueType.Vector1; } }
         public override ConcreteSlotValueType concreteValueType { get { return ConcreteSlotValueType.Vector1; } }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Vector1)
             {

com.unity.shadergraph/Editor/Data/Graphs/Vector2MaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Vector2)
             {

com.unity.shadergraph/Editor/Data/Graphs/Vector3MaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Vector3)
             {

com.unity.shadergraph/Editor/Data/Graphs/Vector4MaterialSlot.cs

             properties.AddShaderProperty(property);
         }
 
-        public override void GetPreviewProperties(ref List<PreviewProperty> properties, string name)
+        public override void GetPreviewProperties(List<PreviewProperty> properties, string name)
         {
             var pp = new PreviewProperty(PropertyType.Vector4)
             {

com.unity.shadergraph/Editor/Data/Nodes/AbstractMaterialNode.cs

                 if (s_TempEdges.Any())
                     continue;
 
-                s.GetPreviewProperties(ref s_TempPreviewProperties, GetVariableNameForSlot(s.id));
+                s.GetPreviewProperties(s_TempPreviewProperties, GetVariableNameForSlot(s.id));
                 for(int i = 0; i < s_TempPreviewProperties.Count; i++)
                 {
                     if (s_TempPreviewProperties[i].name == null)