Cherry-pick ff897ca. rdar://123733686

    Extract a portion of NodeIteratorBase::acceptNode which checks bit flags into its own function
    https://bugs.webkit.org/show_bug.cgi?id=270210
    <rdar://problem/123733686>

    Reviewed by Chris Dumez.

    Extracted matchesWhatToShow out of acceptNode and deployed in TreeWalker::nextNode and
    TreeWalker::previousNode.

    * Source/WebCore/dom/Traversal.cpp:
    (WebCore::NodeIteratorBase::acceptNodeSlowCase):
    * Source/WebCore/dom/Traversal.h:
    (WebCore::NodeIteratorBase::acceptNode):
    (WebCore::NodeIteratorBase::matchesWhatToShow):
    * Source/WebCore/dom/TreeWalker.cpp:
    (WebCore::TreeWalker::previousNode):
    (WebCore::TreeWalker::nextNode):

    Canonical link: https://commits.webkit.org/275468@main

Canonical link: https://commits.webkit.org/272448.862@safari-7618-branch

Source/WebCore/dom/Traversal.cpp

@@ -40,19 +40,15 @@ NodeIteratorBase::NodeIteratorBase(Node& rootNode, unsigned whatToShow, RefPtr<N
 }
 
 // https://dom.spec.whatwg.org/#concept-node-filter
-ExceptionOr<unsigned short> NodeIteratorBase::acceptNode(Node& node)
+ExceptionOr<unsigned short> NodeIteratorBase::acceptNodeSlowCase(Node& node)
 {
+    ASSERT(m_filter);
     if (m_isActive)
         return Exception { ExceptionCode::InvalidStateError, "Recursive filters are not allowed"_s };
 
-    // The bit twiddling here is done to map DOM node types, which are given as integers from
-    // 1 through 14, to whatToShow bit masks.
-    if (!(((1 << (node.nodeType() - 1)) & m_whatToShow)))
+    if (!matchesWhatToShow(node))
         return NodeFilter::FILTER_SKIP;
 
-    if (!m_filter)
-        return NodeFilter::FILTER_ACCEPT;
-
     SetForScope isActive(m_isActive, true);
     auto callbackResult = m_filter->acceptNode(node);
     if (callbackResult.type() == CallbackResultType::ExceptionThrown)

Source/WebCore/dom/Traversal.h

@@ -25,13 +25,12 @@
 #pragma once
 
 #include "ExceptionOr.h"
+#include "Node.h"
+#include "NodeFilter.h"
 #include <wtf/RefPtr.h>
 
 namespace WebCore {
 
-class Node;
-class NodeFilter;
-
 class NodeIteratorBase {
 public:
     Node& root() { return m_root.get(); }
@@ -43,9 +42,23 @@ class NodeIteratorBase {
 
 protected:
     NodeIteratorBase(Node&, unsigned whatToShow, RefPtr<NodeFilter>&&);
-    ExceptionOr<unsigned short> acceptNode(Node&);
+    ExceptionOr<unsigned short> acceptNode(Node& node)
+    {
+        // https://dom.spec.whatwg.org/#concept-node-filter
+        if (!m_filter)
+            return matchesWhatToShow(node) ? NodeFilter::FILTER_ACCEPT : NodeFilter::FILTER_SKIP;
+        return acceptNodeSlowCase(node);
+    }
+
+    bool matchesWhatToShow(const Node& node) const
+    {
+        unsigned nodeMask = 1 << (node.nodeType() - 1);
+        return nodeMask & m_whatToShow;
+    }
 
 private:
+    ExceptionOr<unsigned short> acceptNodeSlowCase(Node&);
+
     Ref<Node> m_root;
     RefPtr<NodeFilter> m_filter;
     unsigned m_whatToShow;

Source/WebCore/dom/TreeWalker.cpp

@@ -183,6 +183,17 @@ ExceptionOr<Node*> TreeWalker::nextSibling()
 
 ExceptionOr<Node*> TreeWalker::previousNode()
 {
+    if (!filter()) {
+        if (m_current.ptr() == &root())
+            return nullptr;
+        for (RefPtr node = NodeTraversal::previous(m_current); node; node = NodeTraversal::previous(*node)) {
+            if (matchesWhatToShow(*node))
+                return setCurrent(node.releaseNonNull());
+            if (node == &root())
+                break;
+        }
+        return nullptr;
+    }
     RefPtr node = m_current.ptr();
     while (node != &root()) {
         while (RefPtr previousSibling = node->previousSibling()) {
@@ -230,6 +241,13 @@ ExceptionOr<Node*> TreeWalker::previousNode()
 
 ExceptionOr<Node*> TreeWalker::nextNode()
 {
+    if (!filter()) {
+        for (RefPtr node = NodeTraversal::next(m_current, &root()); node; node = NodeTraversal::next(*node, &root())) {
+            if (matchesWhatToShow(*node))
+                return setCurrent(node.releaseNonNull());
+        }
+        return nullptr;
+    }
     RefPtr node = m_current.ptr();
 Children:
     while (RefPtr firstChild = node->firstChild()) {