Do not allocate SlotAssignment unless a shadowroot has a slot

third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp

Index: third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp
diff --git a/third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp b/third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp
index 835e03e3aaaba6149be358deb6f62dd29e959dca..c72f2a0cdc84b8557a6fa137266e55be6b0c5142 100644
--- a/third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp
+++ b/third_party/WebKit/Source/core/dom/shadow/ShadowRoot.cpp
@@ -101,6 +101,24 @@ SlotAssignment& ShadowRoot::ensureSlotAssignment() {
   return *m_slotAssignment;
 }
 
+HTMLSlotElement* ShadowRoot::assignedSlotFor(const Node& node) {
+  if (!m_slotAssignment)
+    return nullptr;
+  return m_slotAssignment->findSlot(node);
+}
+
+void ShadowRoot::didAddSlot(HTMLSlotElement& slot) {
+  DCHECK(isV1());
+  ensureSlotAssignment().didAddSlot(slot);
+}
+
+void ShadowRoot::didChangeHostChildSlotName(const AtomicString& oldValue,
+                                            const AtomicString& newValue) {
+  if (!m_slotAssignment)
+    return;
+  m_slotAssignment->didChangeHostChildSlotName(oldValue, newValue);
+}
+
 Node* ShadowRoot::cloneNode(bool, ExceptionState& exceptionState) {
   exceptionState.throwDOMException(NotSupportedError,
                                    "ShadowRoot nodes are not clonable.");