Introduce incognito preference settings.

chrome/browser/extensions/extension_pref_store.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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_EXTENSIONS_EXTENSION_PREF_STORE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_PREF_STORE_H_
 #pragma once
 
+#include <map>
+#include <set>
+
+#include "base/time.h"
 #include "chrome/browser/prefs/value_map_pref_store.h"
 
-// A PrefStore implementation that holds preferences set by extensions.
-class ExtensionPrefStore : public ValueMapPrefStore {
+class ExtensionPrefValueMap;
+
+// A (non-persistent) PrefStore implementation that holds preferences set by
+// extensions.
+// The semantics of the ExtensionPrefStore are:
+// - The precedence of extensions is determined by their installation time.
+//   The extension that has been installed later takes higher precedence.
+// - If two extensions set a value for the same preference, the following
+//   rules determine which value becomes effective (visible).
+// - The effective regular extension pref value is determined by the regular
+//   extension pref value of the extension with the highest precedence.
+// - The effective incognito extension pref value is determined by the incognito
+//   extension pref value of the extension with the highest precedence, unless
+//   another extension with higher precedence overrides it with a regular
+//   extension pref value.
+//
+// The following table illustrates the behavior:
+//   A.reg | A.inc | B.reg | B.inc | E.reg | E.inc
+//     1   |   -   |   -   |   -   |   1   |   1
+//     1   |   2   |   -   |   -   |   1   |   2
+//     1   |   -   |   3   |   -   |   3   |   3
+//     1   |   -   |   -   |   4   |   1   |   4
+//     1   |   2   |   3   |   -   |   3   |   3(!)
+//     1   |   2   |   -   |   4   |   1   |   4
+//     1   |   2   |   3   |   4   |   3   |   4
+// A = extension A, B = extension B, E = effective value
+// .reg = regular value
+// .inc = incognito value
+// Extension B has higher precedence than A.
+//
+// Large parts of ExtensionPrefStore's logic are implemented in
+// ExtensionPrefValueMap.

[Mattias Nissler (ping if slow), 2011/01/05 12:08:07]

Maybe it's useful to put the semantics comment above to the
ExtensionPrefValueMap description and just say here that the ExtensionPrefStore
fetches the effective values from the ExtensionPrefValueMap?

[battre, 2011/01/05 20:23:08]

Done.

+class ExtensionPrefStore : public ValueMapPrefStore,
+                           public PrefStore::Observer {
  public:
-  ExtensionPrefStore();
-  virtual ~ExtensionPrefStore() {}
+  // Constructs an ExtensionPrefStore for a regular or an incognito profile.
+  explicit ExtensionPrefStore(bool incognito_pref_store);
+  virtual ~ExtensionPrefStore();
 
-  // Set an extension preference |value| for |key|. Takes ownership of |value|.
-  void SetExtensionPref(const std::string& key, Value* value);
-
-  // Remove the extension preference value for |key|.
-  void RemoveExtensionPref(const std::string& key);
-
-  // Tell the store it's now fully initialized.
-  void OnInitializationCompleted();
+  // Does not assume ownership of |extension_pref_value_map|.
+  void SetExtensionPrefValueMap(
+      ExtensionPrefValueMap* extension_pref_value_map);

[Mattias Nissler (ping if slow), 2011/01/05 12:08:07]

Why can't we pass this to the constructor?

[battre, 2011/01/05 20:23:08]

Done.

 
  private:
-  // PrefStore overrides:
-  virtual bool IsInitializationComplete() const;
+  // Overrides for PrefStore::Observer:
+  virtual void OnInitializationCompleted();
+  virtual void OnPrefValueChanged(const std::string& key);
 
-  bool initialization_complete_;
+  ExtensionPrefValueMap* extension_pref_value_map_;  // Weak pointer.
+  bool incognito_pref_store_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionPrefStore);
 };
 
-
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_PREF_STORE_H_