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

third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp

Index: third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp b/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
index dc676f01ab385a418fd3391b474cd91876e13293..a3b6c1f5a43ea75ae9462188adbb0226230605ce 100644
--- a/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
+++ b/third_party/WebKit/Source/core/css/invalidation/StyleInvalidator.cpp
@@ -421,7 +421,8 @@ bool StyleInvalidator::Invalidate(Element& element,
     element.SetNeedsStyleRecalc(kSubtreeStyleChange,
                                 StyleChangeReasonForTracing::Create(
                                     StyleChangeReason::kStyleInvalidator));
-  if (recursion_data.InvalidatesSlotted() && isHTMLSlotElement(element))
+  if (recursion_data.InvalidatesSlotted() && isHTMLSlotElement(element) &&
+      toHTMLSlotElement(element).SupportsDistribution())
     InvalidateSlotDistributedElements(toHTMLSlotElement(element),
                                       recursion_data);
 
@@ -434,7 +435,7 @@ bool StyleInvalidator::Invalidate(Element& element,
 void StyleInvalidator::InvalidateSlotDistributedElements(
     HTMLSlotElement& slot,
     const RecursionData& recursion_data) const {
-  for (auto& distributed_node : slot.GetDistributedNodes()) {
+  for (auto& distributed_node : slot.GetDistributedNodesExcludingFallback()) {
     if (distributed_node->NeedsStyleRecalc())
       continue;
     if (!distributed_node->IsElementNode())