Support slotchange event

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/shadow/SlotAssignment.h"
 
 #include "core/HTMLNames.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/NodeTraversal.h"
 #include "core/dom/shadow/ElementShadow.h"
@@ skipping 17 matching lines @@
 void SlotAssignment::resolveAssignment(ShadowRoot& shadowRoot)
 {
     m_assignment.clear();
 
     using Name2Slot = HeapHashMap<AtomicString, Member<HTMLSlotElement>>;
     Name2Slot name2slot;
 
     const HeapVector<Member<HTMLSlotElement>>& slots = shadowRoot.descendantSlots();
 
     for (Member<HTMLSlotElement> slot : slots) {
-        slot->willUpdateDistribution();
+        slot->willUpdateAssignment();
+        slot->willUpdateFallback();
         name2slot.add(slot->name(), slot.get());
     }
 
     for (Node& child : NodeTraversal::childrenOf(*shadowRoot.host())) {
         if (child.isInsertionPoint()) {
             // A re-distribution across v0 and v1 shadow trees is not supported.
             detachNotAssignedNode(child);
             continue;
         }
         if (!child.slottable()) {
             detachNotAssignedNode(child);
             continue;
         }
         AtomicString slotName = child.slotName();
         HTMLSlotElement* slot = name2slot.get(slotName);
         if (slot)
             assign(child, *slot);
         else
             detachNotAssignedNode(child);
     }
 
+    for (auto slot = slots.rbegin(); slot != slots.rend(); ++slot)
+        (*slot)->updateFallbackNodes();
+
+    // For each slot, check if assigned nodes have changed
+    // If so, call fireSlotchange function
+    for (const auto& slot : slots)
+        slot->didUpdateAssignment();
+}
+
+void SlotAssignment::resolveDistribution(ShadowRoot& shadowRoot)
+{
+    const HeapVector<Member<HTMLSlotElement>>& slots = shadowRoot.descendantSlots();
+    for (Member<HTMLSlotElement> slot : slots) {
+        slot->willUpdateDistribution();
+    }
+
+    for (auto slot : slots) {
+        for (auto node : slot->assignedNodes())
+            distribute(*node, *slot);
+    }
+
     // Update each slot's distribution in reverse tree order so that a child slot is visited before its parent slot.
     for (auto slot = slots.rbegin(); slot != slots.rend(); ++slot)
         (*slot)->updateDistributedNodesWithFallback();
     for (const auto& slot : slots)
         slot->didUpdateDistribution();
 }
 
 void SlotAssignment::assign(Node& hostChild, HTMLSlotElement& slot)
 {
     DCHECK(hostChild.isSlotAssignable());
     m_assignment.add(&hostChild, &slot);
     slot.appendAssignedNode(hostChild);
+}
+
+void SlotAssignment::distribute(Node& hostChild, HTMLSlotElement& slot)
+{
+    DCHECK(hostChild.isSlotAssignable());
     if (isHTMLSlotElement(hostChild))
         slot.appendDistributedNodesFrom(toHTMLSlotElement(hostChild));
     else
         slot.appendDistributedNode(hostChild);
+
     if (slot.isChildOfV1ShadowHost())
         slot.parentElementShadow()->setNeedsDistributionRecalc();
 }
 
 DEFINE_TRACE(SlotAssignment)
 {
     visitor->trace(m_assignment);
 }
 
 } // namespace blink