Add a public Blink function to canonicalize and restrict the type of CSS selectors.

public/web/WebSelector.h

Index: public/web/WebSelector.h
diff --git a/public/web/WebSelector.h b/public/web/WebSelector.h
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+/*
+ * Copyright (C) 2013 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WebSelector_h
+#define WebSelector_h
+
+#include "../platform/WebCommon.h"
+
+namespace WebKit {
+
+class WebString;
+
+// Terminology from http://dev.w3.org/csswg/selectors4/#structure.
+enum WebSelectorType {
+    WebSelectorTypeComplex,
+    WebSelectorTypeCompound,
+    // Not yet implemented:
+    // SelectorTypeSimple,
+};
+
+// Returns the value that would be returned from CSSStyleRule.selectorText in the CSSOM for a rule with this selector (which can be a list), if the selector is valid and each component in the list has the type specified in |restriction|.
+// Returns "" for an invalid selector or a selector that doesn't match the restrictions.
+// The canonical form is not guaranteed to stay the same over time.
+WEBKIT_EXPORT WebString canonicalizeSelector(WebString selector, WebSelectorType restriction = WebSelectorTypeComplex);
+
+} // namespace WebKit
+
+#endif