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

Source/web/WebSelector.cpp

Index: Source/web/WebSelector.cpp
diff --git a/Source/web/WebSelector.cpp b/Source/web/WebSelector.cpp
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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.
+ */
+
+#include "config.h"
+#include "WebSelector.h"
+
+#include "../platform/WebString.h"
+#include "core/css/CSSParser.h"
+#include "core/css/CSSSelectorList.h"
+
+using namespace WebCore;
+
+namespace WebKit {
+
+WebString canonicalizeSelector(WebString webSelector, SelectorType restriction)
+{
+    CSSParserContext context(CSSStrictMode);
+    CSSParser parser(context);
+    CSSSelectorList selectorList;
+    parser.parseSelector(webSelector, selectorList);
+
+    if (restriction == SelectorTypeCompound) {
+        for (const CSSSelector* selector = selectorList.first(); selector; selector = selectorList.next(selector)) {
+            if (!selector->isCompound())
+                return WebString();
+        }
+    }
+    return selectorList.selectorsText();
+}
+
+} // namespace WebKit