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..d9265bc7056f8ba6b32cbe4db2c57a650f1e7511 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::slotAdded(HTMLSlotElement& slot) {

[esprehn, 2017/01/17 10:48:18]

DidAddSlot()

[hayato, 2017/01/19 03:13:50]

Done

+  DCHECK(isV1());
+  ensureSlotAssignment().slotAdded(slot);
+}
+
+void ShadowRoot::hostChildSlotNameChanged(const AtomicString& oldValue,

[esprehn, 2017/01/17 10:48:18]

I prefer the did naming.

::DidChangeHostChildSlotName

[hayato, 2017/01/19 03:13:50]

Done

+                                          const AtomicString& newValue) {
+  if (!m_slotAssignment)
+    return;
+  m_slotAssignment->hostChildSlotNameChanged(oldValue, newValue);
+}
+
 Node* ShadowRoot::cloneNode(bool, ExceptionState& exceptionState) {
   exceptionState.throwDOMException(NotSupportedError,
                                    "ShadowRoot nodes are not clonable.");