[import] The first <link rel=import> should win in the cascading order computation.

Source/core/dom/DocumentStyleSheetCollection.cpp

Index: Source/core/dom/DocumentStyleSheetCollection.cpp
diff --git a/Source/core/dom/DocumentStyleSheetCollection.cpp b/Source/core/dom/DocumentStyleSheetCollection.cpp
index c252e12dc8667ad3dad9bc78849a0b5d440eedf3..7d860286da3b63c7f600bbdbb1f34fcc8f9815c7 100644
--- a/Source/core/dom/DocumentStyleSheetCollection.cpp
+++ b/Source/core/dom/DocumentStyleSheetCollection.cpp
@@ -81,6 +81,9 @@ void DocumentStyleSheetCollection::collectStyleSheetsFromCandidates(StyleEngine*
             Document* document = candidate.importedDocument();
             if (!document)
                 continue;
+            if (collector.hasVisited(document))
+                continue;
+            collector.willVisit(document);
             document->styleEngine()->updateStyleSheetsInImport(collector);
             continue;
         }