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 2ffe72b632cb27050fec4286cc4342278e7971e8..c5335b0e526a072c5e5e452d38a894ecaf2bd856 100644
--- a/third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleSheetCandidate.cpp
@@ -88,8 +88,10 @@ 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() || (isHTMLLink() && !isImport() && !isAlternate()))
+            return true;
+    }

[rune, 2016/08/01 09:22:15]

I think I would be leaning towards a behavior where the title attribute is
ignored, effectively making:

  <link rel="stylesheet" title="x">
  <link rel="alternate stylesheet" title="x">

behave as:

  <link rel="stylesheet"> // always enabled
  <link rel="alternate stylesheet"> // never enabled

With the current patch, the former behaves as:

  <link rel="alternate stylesheet" title="x">
  <link rel="alternate stylesheet" title="x">

Have you opened a spec issue?

 
     const AtomicString& title = this->title();
     if (!isEnabledViaScript() && !title.isEmpty() && title != currentPreferrableName)