Styling slot fallback content with ::slotted()

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

Index: third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
index 1961ee2b71074feb66eb0e58fcbea1b8ba00d91b..89a5abb6336cc1a2bce2221d6794c02983864d61 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
@@ -267,8 +267,14 @@ static void MatchHostRules(const Element& element,
 static void MatchSlottedRules(const Element& element,
                               ElementRuleCollector& collector) {
   HTMLSlotElement* slot = element.AssignedSlot();
-  if (!slot)
-    return;
+  if (!slot) {
+    // Check if |element| is a fallback content.
+    Element* parent = element.parentElement();
+    if (!parent || !isHTMLSlotElement(parent) ||
+        !toHTMLSlotElement(parent)->AssignedNodes().IsEmpty())
+      return;
+    slot = toHTMLSlotElement(parent);
+  }

[hayato, 2017/04/13 05:50:40]

I don't think this is correct. Can this handle nested slots?
Please add a test for that.

e.g.
<slot><slot>fallback</slot></slot>

[kochi, 2017/04/14 02:15:13]

Good catch, let me work on it.

 
   HeapVector<Member<ScopedStyleResolver>> resolvers;
   for (; slot; slot = slot->AssignedSlot()) {