Fix assignedNodes({flatten:true}) to return fallback content in document tree

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

Index: third_party/WebKit/Source/core/dom/StyleEngine.cpp
diff --git a/third_party/WebKit/Source/core/dom/StyleEngine.cpp b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
index b19e177637881117d3334b75f792be6cbc922a4a..5d5c90bfc1409ce19b9cb89e62e118b89c87c655 100644
--- a/third_party/WebKit/Source/core/dom/StyleEngine.cpp
+++ b/third_party/WebKit/Source/core/dom/StyleEngine.cpp
@@ -871,7 +871,7 @@ void StyleEngine::ScheduleTypeRuleSetInvalidations(
 }
 
 void StyleEngine::InvalidateSlottedElements(HTMLSlotElement& slot) {
-  for (auto& node : slot.GetDistributedNodes()) {
+  for (auto& node : slot.GetDistributedNodesExcludingFallback()) {

[hayato, 2017/05/18 06:58:25]

Is this correct? Why doesn't this need to invalidate fallback elements?

[kochi, 2017/05/18 07:21:49]

If this is not correct, I'll file another bug.
This should not change from the previous behavior, because the old
GetDistributedNodes() returned its internal distributed_nodes_
which doesn't include fallback content.

     if (node->IsElementNode())
       node->SetNeedsStyleRecalc(kLocalStyleChange,
                                 StyleChangeReasonForTracing::Create(
@@ -912,7 +912,8 @@ void StyleEngine::ScheduleInvalidationsForRuleSets(
   Element* element = ElementTraversal::FirstChild(*stay_within);
   while (element) {
     ScheduleRuleSetInvalidationsForElement(*element, rule_sets);
-    if (invalidate_slotted && isHTMLSlotElement(element))
+    if (invalidate_slotted && isHTMLSlotElement(element) &&
+        toHTMLSlotElement(element)->SupportsDistribution())
       InvalidateSlottedElements(toHTMLSlotElement(*element));
 
     if (element->GetStyleChangeType() < kSubtreeStyleChange)