SELECT element: Introduce light-weight OPTION iterater.

third_party/WebKit/Source/core/html/forms/OptionList.cpp

Index: third_party/WebKit/Source/core/html/forms/OptionList.cpp
diff --git a/third_party/WebKit/Source/core/html/forms/OptionList.cpp b/third_party/WebKit/Source/core/html/forms/OptionList.cpp
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index 0000000000000000000000000000000000000000..06f4f6fe6cef9715d830be5e4e85c81303e910bf
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+++ b/third_party/WebKit/Source/core/html/forms/OptionList.cpp
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+// Copyright 2016 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/html/forms/OptionList.h"
+
+#include "core/dom/ElementTraversal.h"
+#include "core/html/HTMLOptionElement.h"
+#include "core/html/HTMLSelectElement.h"
+
+namespace blink {
+
+void OptionListIterator::advance(HTMLOptionElement* previous)
+{
+    // This function returns only
+    // - An OPTION child of m_select, or
+    // - An OPTION child of an OPTGROUP child of m_select.
+
+    Element* current;
+    if (previous) {
+        DCHECK_EQ(previous->ownerSelectElement(), m_select);
+        current = ElementTraversal::nextSkippingChildren(*previous, m_select);
+    } else {
+        current = ElementTraversal::firstChild(*m_select);
+    }
+    while (current) {
+        if (isHTMLOptionElement(current)) {
+            m_current = toHTMLOptionElement(current);
+            return;
+        }
+        if (isHTMLOptGroupElement(current) && current->parentNode() == m_select) {
+            if ((m_current = Traversal<HTMLOptionElement>::firstChild(*current)))
+                return;
+        }
+        current = ElementTraversal::nextSkippingChildren(*current, m_select);
+    }
+    m_current = nullptr;
+}
+
+} // namespace blink