Add SlottingChildTable in ShadowTree for manual-slotting mode

This CL make Hashmap in ShadowTree to connect nodes to slot in manual slotting mode.

BUG=869308

Change-Id: I59e6bfcb1dc2a91cf3344623bbbf6f7c8545af0a
Reviewed-on: https://chromium-review.googlesource.com/1174133Reviewed-by: Hayato Ito <hayato@chromium.org>
Commit-Queue: Kyoko Muto <kymuto@google.com>
Cr-Commit-Position: refs/heads/master@{#583212}

third_party/WebKit/LayoutTests/shadow-dom/imperative-api.html

@@ -30,7 +30,9 @@ const child2 = document.querySelector('#child2');
 const child3 = document.querySelector('#child3');
 const shadow_root = host.attachShadow({ mode: 'open', slotting: 'manual' });
 const slot1 = document.createElement('slot');
+const slot2 = document.createElement('slot');
 shadow_root.appendChild(slot1);
+shadow_root.appendChild(slot2);
 
 test(() => {
   assert_not_equals(host1.attachShadow({ mode: 'open', slotting: 'manual' }),
@@ -44,8 +46,17 @@ test(() => {
 
 test(() => {
   assert_array_equals(slot1.assignedElements(), []);
+  assert_equals(child1.assignedSlot, null);
+
   slot1.assign([child1]);
+
   assert_array_equals(slot1.assignedNodes(), [child1]);
+  assert_equals(child1.assignedSlot, slot1);
+
+  slot2.assign([child1]);
+  assert_array_equals(slot1.assignedNodes(), []);
+  assert_equals(child1.assignedSlot, slot2);
+
   slot1.assign([child2,child3]);
   assert_array_equals(slot1.assignedNodes(), [child2,child3]);
 }, 'assignedNodes can be used in manual slotting');

third_party/blink/renderer/core/dom/slot_assignment.cc

@@ -242,12 +242,7 @@ void SlotAssignment::RecalcAssignment() {
     HTMLSlotElement* slot = nullptr;
     if (!is_user_agent) {
       if (owner_->IsManualSlotting()) {
-        for (auto candidate : Slots()) {
-          if (candidate->ContainsInAssignedNodesCandidates(child)) {
-            slot = candidate;
-            break;
-          }
-        }
+        slot = FindLastAssignedSlot(const_cast<Node&>(child));
       } else {
         slot = FindSlotByName(child.SlotName());
       }
@@ -344,7 +339,9 @@ HTMLSlotElement* SlotAssignment::FindSlot(const Node& node) const {
     return nullptr;
   if (owner_->IsUserAgent())
     return FindSlotInUserAgentShadow(node);
-  return FindSlotByName(node.SlotName());
+  return owner_->IsManualSlotting()
+             ? FindLastAssignedSlot(const_cast<Node&>(node))
+             : FindSlotByName(node.SlotName());
 }
 
 HTMLSlotElement* SlotAssignment::FindSlotByName(
@@ -363,6 +360,28 @@ HTMLSlotElement* SlotAssignment::FindSlotInUserAgentShadow(
   return user_agent_default_slot;
 }
 
+HTMLSlotElement* SlotAssignment::FindLastAssignedSlot(Node& node) const {
+  auto it = child_assigned_slot_history_.find(&node);
+  if (it == child_assigned_slot_history_.end())
+    return nullptr;
+  return it.Get()->value.back();
+}
+
+void SlotAssignment::InsertSlotInChildSlotMap(
+    HTMLSlotElement& slot,
+    const HeapVector<Member<Node>>& nodes) {
+  for (Member<Node> child : nodes) {
+    auto it = child_assigned_slot_history_.find(child);
+    if (it == child_assigned_slot_history_.end()) {
+      HeapVector<Member<HTMLSlotElement>> tmp;
+      tmp.push_back(slot);
+      child_assigned_slot_history_.Set(child, tmp);
+    } else {
+      it.Get()->value.push_back(slot);
+    }
+  }
+}
+
 void SlotAssignment::CollectSlots() {
   DCHECK(needs_collect_slots_);
   slots_.clear();
@@ -389,6 +408,7 @@ void SlotAssignment::Trace(blink::Visitor* visitor) {
   visitor->Trace(slots_);
   visitor->Trace(slot_map_);
   visitor->Trace(owner_);
+  visitor->Trace(child_assigned_slot_history_);
 }
 
 }  // namespace blink

third_party/blink/renderer/core/dom/slot_assignment.h

@@ -44,6 +44,9 @@ class SlotAssignment final : public GarbageCollected<SlotAssignment> {
 
   bool FindHostChildBySlotName(const AtomicString& slot_name) const;
 
+  void InsertSlotInChildSlotMap(HTMLSlotElement& slot,
+                                const HeapVector<Member<Node>>& nodes);
+
   void Trace(blink::Visitor*);
 
   // For Incremental Shadow DOM
@@ -64,6 +67,8 @@ class SlotAssignment final : public GarbageCollected<SlotAssignment> {
 
   HTMLSlotElement* FindSlotInUserAgentShadow(const Node&) const;
 
+  HTMLSlotElement* FindLastAssignedSlot(Node&) const;
+
   void CollectSlots();
   HTMLSlotElement* GetCachedFirstSlotWithoutAccessingNodeTree(
       const AtomicString& slot_name);
@@ -78,6 +83,8 @@ class SlotAssignment final : public GarbageCollected<SlotAssignment> {
 
   HeapVector<Member<HTMLSlotElement>> slots_;
   Member<TreeOrderedMap> slot_map_;
+  HeapHashMap<Member<Node>, HeapVector<Member<HTMLSlotElement>>>
+      child_assigned_slot_history_;
   WeakMember<ShadowRoot> owner_;
   unsigned needs_collect_slots_ : 1;
   unsigned needs_assignment_recalc_ : 1;  // For Incremental Shadow DOM

third_party/blink/renderer/core/html/html_slot_element.cc

@@ -190,6 +190,8 @@ const HeapVector<Member<Element>> HTMLSlotElement::AssignedElementsForBinding(
 }
 
 void HTMLSlotElement::assign(HeapVector<Member<Node>> nodes) {
+  ContainingShadowRoot()->GetSlotAssignment().InsertSlotInChildSlotMap(*this,
+                                                                       nodes);
   ContainingShadowRoot()->GetSlotAssignment().SetNeedsAssignmentRecalc();
   assigned_nodes_candidates_.clear();
   for (Member<Node> child : nodes) {