Improved background serialization

src/AngleSharp.Css/Declarations/BackgroundDeclaration.cs

@@ -30,7 +30,7 @@ namespace AngleSharp.Css.Declarations
             PropertyNames.BackgroundColor,
         };
 
-        sealed class BackgroundValueConverter : IValueConverter
+        sealed class BackgroundAggregator : IValueAggregator, IValueConverter
         {
             public ICssValue Convert(StringSource source)
             {
@@ -113,7 +113,7 @@ namespace AngleSharp.Css.Declarations
                         }
                     }
                     while (pos != source.Index);
-                    
+
                     layers.Add(new CssBackgroundLayerValue(
                         image,
                         position,
@@ -126,13 +126,6 @@ namespace AngleSharp.Css.Declarations
 
                 return new CssBackgroundValue(new CssListValue(layers.OfType<ICssValue>().ToArray()), color);
             }
-        }
-
-        sealed class BackgroundAggregator : IValueAggregator, IValueConverter
-        {
-            private static readonly IValueConverter converter = new BackgroundValueConverter();
-
-            public ICssValue Convert(StringSource source) => converter.Convert(source);
 
             public ICssValue Merge(ICssValue[] values)
             {
@@ -144,7 +137,6 @@ namespace AngleSharp.Css.Declarations
                 var origin = GetList(values[5]);
                 var clip = GetList(values[6]);
                 var color = values[7];
-
                 var layers = CreateLayers(image, attachment, clip, position, origin, repeat, size);
 
                 if (color != null || layers != null)

src/AngleSharp.Css/Declarations/BackgroundPositionDeclaration.cs

@@ -52,10 +52,6 @@ namespace AngleSharp.Css.Declarations
 
                     return new CssListValue(points);
                 }
-                else if (values[0] is CssInitialValue && values[1] is CssInitialValue)
-                {
-                    return new CssInitialValue(InitialValues.BackgroundPositionDecl);
-                }
 
                 return null;
             }
@@ -73,14 +69,6 @@ namespace AngleSharp.Css.Declarations
                         new CssListValue(y),
                     };
                 }
-                else if (value is CssInitialValue)
-                {
-                    return new ICssValue[]
-                    {
-                        new CssInitialValue(InitialValues.BackgroundPositionXDecl),
-                        new CssInitialValue(InitialValues.BackgroundPositionYDecl),
-                    };
-                }
 
                 return null;
             }

src/AngleSharp.Css/Declarations/BackgroundRepeatDeclaration.cs

@@ -52,10 +52,6 @@ namespace AngleSharp.Css.Declarations
 
                     return new CssListValue(repeats);
                 }
-                else if (values[0] is CssInitialValue && values[1] is CssInitialValue)
-                {
-                    return new CssInitialValue(InitialValues.BackgroundRepeatDecl);
-                }
 
                 return null;
             }
@@ -73,14 +69,6 @@ namespace AngleSharp.Css.Declarations
                         new CssListValue(v),
                     };
                 }
-                else if (value is CssInitialValue)
-                {
-                    return new ICssValue[]
-                    {
-                        new CssInitialValue(InitialValues.BackgroundRepeatHorizontalDecl),
-                        new CssInitialValue(InitialValues.BackgroundRepeatVerticalDecl),
-                    };
-                }
 
                 return null;
             }

src/AngleSharp.Css/Extensions/DeclarationInfoExtensions.cs

@@ -47,11 +47,16 @@ namespace AngleSharp.Css
             if (value is ICssRawValue || value is CssChildValue)
             {
                 var child = new CssChildValue(value);
-                return Enumerable.Repeat(child, longhands.Length).ToArray();
+                return Enumerable
+                    .Repeat(child, longhands.Length)
+                    .ToArray();
             }
             else if (value is CssInitialValue)
             {
-                return longhands.Select(name => factory.Create(name)?.InitialValue).ToArray();
+                return longhands
+                    .Select(name => new CssInitialValue(factory.Create(name)?.InitialValue))
+                    .OfType<ICssValue>()
+                    .ToArray();
             }
 
             return info.Aggregator?.Split(value);