[dom] support iterable<> NodeList

third_party/WebKit/Source/core/dom/NodeList.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 "config.h"
+#include "core/dom/NodeList.h"
+
+namespace blink {
+
+namespace {
+
+class NodeListIterationSource final : public ValueIterable<Node*>::IterationSource {
+public:
+    explicit NodeListIterationSource(NodeList* nodeList)

[esprehn, 2015/10/03 05:07:45]

reference

[caitp (gmail), 2015/10/03 15:46:45]

Done.

+        : m_nodeList(nodeList)
+    {
+    }
+
+    bool next(ScriptState* scriptState, Node*& value, ExceptionState& exceptionState) override
+    {
+        if (m_index >= m_nodeList->length()) {

[esprehn, 2015/10/03 05:07:45]

accessing length causes us to cache the entire contents which seems unnecessary.

+            value = nullptr;
+            return false;
+        }
+        value = m_nodeList->item(m_index);

[esprehn, 2015/10/03 05:07:45]

accessing out of bounds always returns a nullptr, this whole function can be
written as:

value = m_nodeList->item(m_index);
return value != nullptr;

[caitp (gmail), 2015/10/03 15:46:45]

Done.

There's a presubmit rule preventing comparisons with nullptr, so it's written as
`!!value`, which is kind of weird. But I guess if people prefer that?

+        return true;
+    }
+
+    DEFINE_INLINE_VIRTUAL_TRACE()
+    {
+        visitor->trace(m_nodeList);
+        ValueIterable<Node*>::IterationSource::trace(visitor);
+    }
+
+private:
+    const RefPtrWillBeMember<NodeList> m_nodeList;
+};
+
+} // namespace
+
+ValueIterable<Node*>::IterationSource* NodeList::startIteration(ScriptState*, ExceptionState&)
+{
+    return new NodeListIterationSource(this);

[esprehn, 2015/10/03 05:07:45]

*this

+}
+
+} // namespace blink