Create a DefaultPrefStore to hold registered application-default preference v...

chrome/browser/prefs/pref_service.h

Index: chrome/browser/prefs/pref_service.h
===================================================================
--- chrome/browser/prefs/pref_service.h	(revision 59196)
+++ chrome/browser/prefs/pref_service.h	(working copy)
@@ -28,14 +28,13 @@
   class Preference {
    public:
 
-    // The type of the preference is determined by the type of |default_value|.
-    // Therefore, the type needs to be a boolean, integer, real, string,
+    // The type of the preference is determined by the type with which it is
+    // registered. This type needs to be a boolean, integer, real, string,
     // dictionary (a branch), or list.  You shouldn't need to construct this on
-    // your own, use the PrefService::Register*Pref methods instead.
-    // |default_value| will be owned by the Preference object.
-    Preference(PrefValueStore* pref_value_store,
+    // your own; use the PrefService::Register*Pref methods instead.
+    Preference(const PrefService* service,
                const char* name,
-               Value* default_value);
+               Value::ValueType type);
     ~Preference() {}
 
     Value::ValueType type() const { return type_; }
@@ -44,13 +43,10 @@
     // browser.window_placement).
     const std::string name() const { return name_; }
 
-    // Returns the value of the Preference.  If there is no user specified
-    // value, it returns the default value.
+    // Returns the value of the Preference, falling back to the registered
+    // default value if no other has been set.
     const Value* GetValue() const;
 
-    // Returns true if the current value matches the default value.
-    bool IsDefaultValue() const;
-
     // Returns true if the Preference is managed, i.e. set by an admin policy.
     // Since managed prefs have the highest priority, this also indicates
     // whether the pref is actually being controlled by the policy setting.
@@ -72,6 +68,11 @@
     // user setting, and not by any higher-priority source.
     bool IsUserControlled() const;
 
+    // Returns true if the Preference is currently using its default value,
+    // and has not been set by any higher-priority source (even with the same
+    // value).
+    bool IsDefaultValue() const;
+
     // Returns true if the user can change the Preference value, which is the
     // case if no higher-priority source than the user store controls the
     // Preference.
@@ -82,10 +83,9 @@
 
     Value::ValueType type_;
     std::string name_;
-    scoped_ptr<Value> default_value_;
 
-    // A reference to the pref service's pref_value_store_.
-    PrefValueStore* pref_value_store_;
+    // Reference to the PrefService in which this pref was created.
+    const PrefService* pref_service_;
 
     DISALLOW_COPY_AND_ASSIGN(Preference);
   };
@@ -100,8 +100,8 @@
 
   // Convenience factory method for use in unit tests. Creates a new
   // PrefService that uses a PrefValueStore with user preferences at the given
-  // |pref_filename|, and no other PrefStores (i.e., no other types of
-  // preferences).
+  // |pref_filename|, a default PrefStore, and no other PrefStores (i.e., no
+  // other types of preferences).
   static PrefService* CreateUserPrefService(const FilePath& pref_filename);
 
   // This constructor is primarily used by tests. The |pref_value_store|
@@ -171,7 +171,9 @@
   void ClearPref(const char* path);
 
   // If the path is valid (i.e., registered), update the pref value in the user
-  // prefs.
+  // prefs. Seting a null value on a preference of List or Dictionary type is
+  // equivalent to removing the user value for that preference, allowing the
+  // default value to take effect unless another value takes precedence.
   void Set(const char* path, const Value& value);
   void SetBoolean(const char* path, bool value);
   void SetInteger(const char* path, int value);
@@ -219,6 +221,8 @@
 
   PrefNotifier* pref_notifier() const { return pref_notifier_.get(); }
 
+  PrefValueStore* pref_value_store() const { return pref_value_store_.get(); }
+
  protected:
   // The PrefNotifier handles registering and notifying preference observers.
   // It is created and owned by this PrefService. Subclasses may access it for
@@ -227,13 +231,17 @@
 
  private:
   // Add a preference to the PreferenceMap.  If the pref already exists, return
-  // false.  This method takes ownership of |pref|.
-  void RegisterPreference(Preference* pref);
+  // false.  This method takes ownership of |default_value|.
+  void RegisterPreference(const char* path, Value* default_value);
 
   // Returns a copy of the current pref value.  The caller is responsible for
   // deleting the returned object.
   Value* GetPrefCopy(const char* pref_name);
 
+  // Sets the value for this pref path in the user pref store and informs the
+  // PrefNotifier of the change.
+  void SetUserPrefValue(const char* path, Value* new_value);
+
   // Load from disk.  Returns a non-zero error code on failure.
   PrefStore::PrefReadError LoadPersistentPrefs();