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diff --git a/Source/WebCore/page/FeatureObserver.h b/Source/WebCore/page/FeatureObserver.h
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+++ b/Source/WebCore/page/FeatureObserver.h
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+/*
+ * Copyright (C) 2012 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:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY GOOGLE INC. ``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 APPLE COMPUTER, INC. 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 FeatureObserver_h
+#define FeatureObserver_h
+
+#include <wtf/Noncopyable.h>
+
+namespace WebCore {
+
+class DOMWindow;
+
+class FeatureObserver {
+    WTF_MAKE_NONCOPYABLE(FeatureObserver);
+public:
+    FeatureObserver();
+    ~FeatureObserver();
+
+    enum Feature {
+        PageDestruction,
+        LegacyNotifications,
+        LegacyBlobBuilder,
+        PrefixedIndexedDB,
+        // Add new features above this line.
+        NumberOfFeatures, // This enum value must be last.
+    };
+
+    static void observe(DOMWindow*, Feature);
+
+private:
+    void didObserve(Feature feature)
+    {
+        COMPILE_ASSERT(sizeof(m_featureMask) * 8 >= NumberOfFeatures, FeaturesMustNotOverflowBitmask);
+        ASSERT(feature != PageDestruction); // PageDestruction is reserved as a scaling factor.
+        ASSERT(feature < NumberOfFeatures);
+        m_featureMask |= 1 << static_cast<int>(feature);
+    }
+
+    int m_featureMask;
+};
+
+} // namespace WebCore
+    
+#endif // FeatureObserver_h