Introduce incognito preference settings.

chrome/browser/prefs/default_pref_store.h

 // Copyright (c) 2010 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 CHROME_BROWSER_PREFS_DEFAULT_PREF_STORE_H_
 #define CHROME_BROWSER_PREFS_DEFAULT_PREF_STORE_H_
 #pragma once
 
 #include <map>
+#include <string>
 
 #include "base/basictypes.h"
 #include "chrome/browser/prefs/value_map_pref_store.h"
 
 // This PrefStore keeps track of default preference values set when a
 // preference is registered with the PrefService.
 class DefaultPrefStore : public ValueMapPrefStore {
  public:
   DefaultPrefStore() {}
   virtual ~DefaultPrefStore() {}
 
   // Stores a new |value| for |key|. Assumes ownership of |value|.
   void SetDefaultValue(const std::string& key, Value* value) {
+    CHECK(GetValue(key, NULL) == READ_NO_VALUE);
     SetValue(key, value);
   }
 
+  // Returns the registered type for |key| or Value::TYPE_NULL if the |key|
+  // has not been registered.
+  Value::ValueType GetType(const std::string& key) const {
+    Value* value;
+    return GetValue(key, &value) == READ_OK ? value->GetType()
+                                            : Value::TYPE_NULL;
+  }
+
  private:
   DISALLOW_COPY_AND_ASSIGN(DefaultPrefStore);
 };
 
 #endif  // CHROME_BROWSER_PREFS_DEFAULT_PREF_STORE_H_