Fixed regression caused by use test for recursion

- added image broken by regression to tests (__Flag_of_the_United_States)
- added some passing issue specific tests to image comparison tests

Source/Document Structure/SvgUse.cs

@@ -16,7 +16,7 @@ namespace Svg
             set { this._referencedElement = value; }
         }
 
-        static private bool ElementReferencesUri(SvgElement element, List<Uri> elementUris)
+        private bool ElementReferencesUri(SvgElement element, List<Uri> elementUris)
         {
             var useElement = element as SvgUse;
             if (useElement != null)
@@ -26,7 +26,11 @@ namespace Svg
                     return true;
                 }
                 // also detect cycles in referenced elements
-                elementUris.Add(useElement.ReferencedElement);
+                var refElement = this.OwnerDocument.IdManager.GetElementById(useElement.ReferencedElement);
+                if (refElement is SvgUse)
+                {
+                    elementUris.Add(useElement.ReferencedElement);
+                }
                 return useElement.ReferencedElementReferencesUri(elementUris);
             }
             var groupElement = element as SvgGroup;

Tests/Svg.UnitTests/ImageComparisonTest.cs

@@ -86,9 +86,16 @@ namespace Svg.UnitTests
             try
             {
                 doc = SvgDocument.Open(svgPath);
-                var img = new Bitmap(480, 360);
-                doc.Draw(img);
-                svgImage = img;
+                if (fileName.StartsWith("__"))
+                {
+                    svgImage = doc.Draw();
+                }
+                else
+                {
+                    var img = new Bitmap(480, 360);
+                    doc.Draw(img);
+                    svgImage = img;
+                }
             }
             catch (Exception)
             {

Tests/Svg.UnitTests/PassingTests.csv

@@ -157,3 +157,11 @@ text-text-11-t
 text-tref-01-b
 text-tspan-01-b
 types-basic-01-f
+__Flag_of_the_United_States
+__issue-064-02
+__issue-279-01
+__issueViewBox
+__pull_request-373-01
+__pull_request-374-01
+__Telefunken_FuBK_test_pattern
+__title
\ No newline at end of file