Revert of Support slot element's fallback content feature

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

Index: third_party/WebKit/Source/core/dom/shadow/ComposedTreeTraversal.cpp
diff --git a/third_party/WebKit/Source/core/dom/shadow/ComposedTreeTraversal.cpp b/third_party/WebKit/Source/core/dom/shadow/ComposedTreeTraversal.cpp
index a1c84831ebb6d643c091260743940a6577630f56..4050ea183c938d13aa89f4064d03f58a994ba969 100644
--- a/third_party/WebKit/Source/core/dom/shadow/ComposedTreeTraversal.cpp
+++ b/third_party/WebKit/Source/core/dom/shadow/ComposedTreeTraversal.cpp
@@ -38,11 +38,6 @@
     return node.isElementNode() ? toElement(node).shadow() : nullptr;
 }
 
-static inline bool canBeDistributedToInsertionPoint(const Node& node)
-{
-    return node.isInV0ShadowTree() || node.isChildOfV0ShadowHost();
-}
-
 Node* ComposedTreeTraversal::traverseChild(const Node& node, TraversalDirection direction)
 {
     ElementShadow* shadow = shadowFor(node);
@@ -57,23 +52,13 @@
 {
     if (!node)
         return nullptr;
-    for (const Node* sibling = node; sibling; sibling = (direction == TraversalDirectionForward ? sibling->nextSibling() : sibling->previousSibling())) {
-        if (isHTMLSlotElement(*sibling)) {
-            const HTMLSlotElement& slot = toHTMLSlotElement(*sibling);
-            if (Node* found = (direction == TraversalDirectionForward ? slot.firstDistributedNode() : slot.lastDistributedNode()))
-                return found;
-            continue;
-        }
-        if (node->isInV0ShadowTree())
-            return v0ResolveDistributionStartingAt(*sibling, direction);
-        return const_cast<Node*>(sibling);
-    }
-    return nullptr;
+    if (node->isInShadowTree() && node->containingShadowRoot()->isV1())
+        return v1ResolveDistributionStartingAt(*node, direction);
+    return v0ResolveDistributionStartingAt(*node, direction);
 }
 
 Node* ComposedTreeTraversal::v0ResolveDistributionStartingAt(const Node& node, TraversalDirection direction)
 {
-    ASSERT(!isHTMLSlotElement(node));
     for (const Node* sibling = &node; sibling; sibling = (direction == TraversalDirectionForward ? sibling->nextSibling() : sibling->previousSibling())) {
         if (!isActiveInsertionPoint(*sibling))
             return const_cast<Node*>(sibling);
@@ -85,6 +70,18 @@
     return nullptr;
 }
 
+Node* ComposedTreeTraversal::v1ResolveDistributionStartingAt(const Node& node, TraversalDirection direction)
+{
+    for (const Node* sibling = &node; sibling; sibling = (direction == TraversalDirectionForward ? sibling->nextSibling() : sibling->previousSibling())) {
+        if (!isHTMLSlotElement(*sibling))
+            return const_cast<Node*>(sibling);
+        const HTMLSlotElement& slot = toHTMLSlotElement(*sibling);
+        if (Node* found = (direction == TraversalDirectionForward ? slot.firstDistributedNode() : slot.lastDistributedNode()))
+            return found;
+    }
+    return nullptr;
+}
+
 static HTMLSlotElement* finalDestinationSlotFor(const Node& node)
 {
     HTMLSlotElement* slot = node.assignedSlot();
@@ -96,53 +93,70 @@
     return slot;
 }
 
+Node* ComposedTreeTraversal::traverseSiblings(const Node& node, TraversalDirection direction)
+{
+    Node* parent = node.parentNode();
+    if (!parent)
+        return nullptr;
+    if (parent->isElementNode()) {
+        if (ElementShadow* shadow = toElement(parent)->shadow()) {
+            if (shadow->isV1()) {
+                return v1TraverseSiblings(node, direction);
+            }
+        }
+    }
+    return v0TraverseSiblings(node, direction);
+}
+
 // TODO(hayato): This may return a wrong result for a node which is not in a
 // document composed tree.  See ComposedTreeTraversalTest's redistribution test for details.
-Node* ComposedTreeTraversal::traverseSiblings(const Node& node, TraversalDirection direction)
-{
-    if (node.isChildOfV1ShadowHost())
-        return traverseSiblingsForV1HostChild(node, direction);
-
-    if (shadowWhereNodeCanBeDistributed(node))
-        return traverseSiblingsForV0Distribution(node, direction);
-
+Node* ComposedTreeTraversal::v0TraverseSiblings(const Node& node, TraversalDirection direction)
+{
+    if (!shadowWhereNodeCanBeDistributed(node))
+        return traverseSiblingsOrShadowInsertionPointSiblings(node, direction);
+
+    const InsertionPoint* finalDestination = resolveReprojection(&node);
+    if (!finalDestination)
+        return nullptr;
+    if (Node* found = (direction == TraversalDirectionForward ? finalDestination->distributedNodeNextTo(&node) : finalDestination->distributedNodePreviousTo(&node)))
+        return found;
+    return traverseSiblings(*finalDestination, direction);
+}
+
+Node* ComposedTreeTraversal::v1TraverseSiblings(const Node& node, TraversalDirection direction)
+{
+    HTMLSlotElement* slot = finalDestinationSlotFor(node);
+    if (!slot)
+        return resolveDistributionStartingAt(direction == TraversalDirectionForward ? node.nextSibling() : node.previousSibling(), direction);
+    if (Node* siblingInDistributedNodes = (direction == TraversalDirectionForward ? slot->distributedNodeNextTo(node) : slot->distributedNodePreviousTo(node)))
+        return siblingInDistributedNodes;
+    return v1TraverseSiblings(*slot, direction);
+}
+
+Node* ComposedTreeTraversal::traverseSiblingsOrShadowInsertionPointSiblings(const Node& node, TraversalDirection direction)
+{
     if (Node* found = resolveDistributionStartingAt(direction == TraversalDirectionForward ? node.nextSibling() : node.previousSibling(), direction))
         return found;
 
-    if (!node.isInV0ShadowTree())
-        return nullptr;
-
-    // For v0 older shadow tree
     if (node.parentNode() && node.parentNode()->isShadowRoot()) {
         ShadowRoot* parentShadowRoot = toShadowRoot(node.parentNode());
         if (!parentShadowRoot->isYoungest()) {
             HTMLShadowElement* assignedInsertionPoint = parentShadowRoot->shadowInsertionPointOfYoungerShadowRoot();
             ASSERT(assignedInsertionPoint);
-            return traverseSiblings(*assignedInsertionPoint, direction);
+            return traverseSiblingsOrShadowInsertionPointSiblings(*assignedInsertionPoint, direction);
         }
     }
     return nullptr;
 }
 
-Node* ComposedTreeTraversal::traverseSiblingsForV1HostChild(const Node& node, TraversalDirection direction)
-{
-    HTMLSlotElement* slot = finalDestinationSlotFor(node);
-    if (!slot)
-        return nullptr;
-    if (Node* siblingInDistributedNodes = (direction == TraversalDirectionForward ? slot->distributedNodeNextTo(node) : slot->distributedNodePreviousTo(node)))
-        return siblingInDistributedNodes;
-    return traverseSiblings(*slot, direction);
-}
-
-Node* ComposedTreeTraversal::traverseSiblingsForV0Distribution(const Node& node, TraversalDirection direction)
-{
-    const InsertionPoint* finalDestination = resolveReprojection(&node);
-    if (!finalDestination)
-        return nullptr;
-    if (Node* found = (direction == TraversalDirectionForward ? finalDestination->distributedNodeNextTo(&node) : finalDestination->distributedNodePreviousTo(&node)))
-        return found;
-    return traverseSiblings(*finalDestination, direction);
-
+static ElementShadow* parentElementShadow(const Node& node)
+{
+    Node* parent = node.parentNode();
+    if (!parent)
+        return nullptr;
+    if (parent->isElementNode())
+        return toElement(parent)->shadow();
+    return nullptr;
 }
 
 ContainerNode* ComposedTreeTraversal::traverseParent(const Node& node, ParentTraversalDetails* details)
@@ -151,49 +165,43 @@
     if (node.isPseudoElement())
         return node.parentOrShadowHostNode();
 
-    if (node.isChildOfV1ShadowHost()) {
-        HTMLSlotElement* slot = finalDestinationSlotFor(node);
-        if (!slot)
+    ElementShadow* shadow = parentElementShadow(node);
+    if (shadow && shadow->isV1())
+        return v1TraverseParent(node);
+    if (shadowWhereNodeCanBeDistributed(node))
+        return v0TraverseParent(node, details);
+    return traverseParentOrHost(node);
+}
+
+ContainerNode* ComposedTreeTraversal::v1TraverseParent(const Node& node)
+{
+    HTMLSlotElement* slot = finalDestinationSlotFor(node);
+    if (!slot)
+        return nullptr;
+    if (parentElementShadow(*slot)) {
+        // The node is distributed to the |slot|, however, |slot|, which is a
+        // child of a shadow host, is not assigned to any slots.
+        return nullptr;
+    }
+    return traverseParentOrHost(*slot);
+}
+
+ContainerNode* ComposedTreeTraversal::v0TraverseParent(const Node& node, ParentTraversalDetails* details)
+{
+    if (const InsertionPoint* insertionPoint = resolveReprojection(&node)) {
+        if (details)
+            details->didTraverseInsertionPoint(insertionPoint);
+        // The node is distributed. But the distribution was stopped at this insertion point.
+        if (shadowWhereNodeCanBeDistributed(*insertionPoint))
             return nullptr;
-        return traverseParent(*slot);
-    }
-
-    Element* parent = node.parentElement();
-    if (parent && isHTMLSlotElement(parent)) {
-        HTMLSlotElement& slot = toHTMLSlotElement(*parent);
-        if (!slot.getAssignedNodes().isEmpty())
-            return nullptr;
-        return traverseParent(slot, details);
-    }
-
-    if (canBeDistributedToInsertionPoint(node))
-        return traverseParentForV0(node, details);
-
-    ASSERT(!shadowWhereNodeCanBeDistributed(node));
-    return traverseParentOrHost(node);
-}
-
-ContainerNode* ComposedTreeTraversal::traverseParentForV0(const Node& node, ParentTraversalDetails* details)
-{
-    if (shadowWhereNodeCanBeDistributed(node)) {
-        if (const InsertionPoint* insertionPoint = resolveReprojection(&node)) {
-            if (details)
-                details->didTraverseInsertionPoint(insertionPoint);
-            // The node is distributed. But the distribution was stopped at this insertion point.
-            if (shadowWhereNodeCanBeDistributed(*insertionPoint))
-                return nullptr;
-            return traverseParent(*insertionPoint);
-        }
-        return nullptr;
-    }
-    ContainerNode* parent = traverseParentOrHost(node);
-    if (isActiveInsertionPoint(*parent))
-        return nullptr;
-    return parent;
-}
-
-ContainerNode* ComposedTreeTraversal::traverseParentOrHost(const Node& node)
-{
+        return traverseParentOrHost(*insertionPoint);
+    }
+    return nullptr;
+}
+
+inline ContainerNode* ComposedTreeTraversal::traverseParentOrHost(const Node& node)
+{
+    // TODO(hayato): Support fallback contents of slots. The parent can be a slot.
     ContainerNode* parent = node.parentNode();
     if (!parent)
         return nullptr;
@@ -203,7 +211,10 @@
     ASSERT(!shadowRoot->shadowInsertionPointOfYoungerShadowRoot());
     if (!shadowRoot->isYoungest())
         return nullptr;
-    return shadowRoot->host();
+    Element* host = shadowRoot->host();
+    if (isActiveInsertionPoint(*host))
+        return nullptr;
+    return host;
 }
 
 Node* ComposedTreeTraversal::childAt(const Node& node, unsigned index)