Implement a simple version of SelectorQuery.

third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.cpp

Index: third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.cpp
diff --git a/third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.cpp b/third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..e81a9701f735931ce72585ec16f13c36d941350a
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.cpp
@@ -0,0 +1,27 @@
+// 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/query/SelectorClassMatcher.h"
+
+#include "core/dom/ContainerNode.h"
+#include "core/dom/Element.h"
+
+namespace blink {
+
+SelectorClassMatcher::SelectorClassMatcher(const AtomicString& className)
+    : m_className(className)
+{
+}
+
+SelectorClassMatcher::~SelectorClassMatcher()
+{
+}
+
+bool SelectorClassMatcher::match(Element& element, ContainerNode& rootNode) const
+{
+    return element.hasClass() && element.classNames().contains(m_className);
+}
+
+}