Implement a simple version of SelectorQuery.

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

Index: third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.h
diff --git a/third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.h b/third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..8165a3dab1bad0651b494c3265f326b827ee4187
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/query/SelectorClassMatcher.h
@@ -0,0 +1,25 @@
+// 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.
+
+#ifndef SelectorClassMatcher_h
+#define SelectorClassMatcher_h
+
+#include "core/dom/query/SelectorMatcher.h"
+#include "wtf/text/AtomicString.h"
+
+namespace blink {
+
+class SelectorClassMatcher final : public SelectorMatcher {
+public:
+    explicit SelectorClassMatcher(const AtomicString& className);
+    ~SelectorClassMatcher() override;
+
+    bool match(Element&, ContainerNode& rootNode) const override;
+private:
+    AtomicString m_className;
+};
+
+}
+
+#endif