Allow <link rel=stylesheet> in a connected shadow tree

third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp

Index: third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp b/third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp
index e2f7b233e5925814a20eec219fe4a5e04889c29f..d1a15e49a39c50c834b1014a363b69cee214cdb8 100644
--- a/third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp
@@ -88,8 +88,12 @@ bool StyleSheetCandidate::canBeActivated(const String& currentPreferrableName) c
     if (!sheet || sheet->disabled() || !sheet->isCSSStyleSheet())
         return false;
 
-    if (sheet->ownerNode() && sheet->ownerNode()->isInShadowTree())
-        return true;
+    if (sheet->ownerNode() && sheet->ownerNode()->isInShadowTree()) {
+        if (isCSSStyle())
+            return true;
+        if (isHTMLLink() && !isImport())
+            return !isAlternate();
+    }
 
     const AtomicString& title = this->title();
     if (!isEnabledViaScript() && !title.isEmpty() && title != currentPreferrableName)