Warn developers about deprecated features only once per page-load.

Source/core/page/PageConsole.h

 /*
  * Copyright (C) 2013 Apple 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
@@ skipping 14 matching lines @@
  * (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 PageConsole_h
 #define PageConsole_h
 
 #include "ConsoleTypes.h"
 #include "ScriptCallStack.h"
 #include "ScriptState.h"
+#include <wtf/BitVector.h>
 #include <wtf/Forward.h>
 #include <wtf/PassOwnPtr.h>
 
 namespace WebCore {
 
 class Document;
 class Page;
 
 class PageConsole {
 public:
+    enum DeprecatedFeature {
+        PrefixedContentSecurityPolicyHeader,
+
+        // Add newly deprecated features above this line.
+        NumberOfFeatures, // Sentinel.
+    };
+
     static PassOwnPtr<PageConsole> create(Page* page) { return adoptPtr(new PageConsole(page)); }
     virtual ~PageConsole();
 
     void addMessage(MessageSource, MessageLevel, const String& message, const String& sourceURL, unsigned lineNumber, PassRefPtr<ScriptCallStack> = 0, ScriptState* = 0, unsigned long requestIdentifier = 0);
     void addMessage(MessageSource, MessageLevel, const String& message, PassRefPtr<ScriptCallStack>);
     void addMessage(MessageSource, MessageLevel, const String& message, unsigned long requestIdentifier = 0, Document* = 0);
 
+    static void reportDeprecation(Document*, DeprecatedFeature);
+
     static void mute();
     static void unmute();
 
 private:
     PageConsole(Page*);
 
+    void addDeprecationMessage(DeprecatedFeature);
+
     Page* page() { return m_page; };
 
     Page* m_page;
+    BitVector m_deprecationNotifications;
 };
 
 } // namespace WebCore
 
 #endif // PageConsole_h