1 files changed, 89 insertions, 2 deletions

diff --git a/chrome/browser/prefs/scoped_user_pref_update.h b/chrome/browser/prefs/scoped_user_pref_update.h
index 8992d09..69572fa 100644
--- a/chrome/browser/prefs/scoped_user_pref_update.h
+++ b/chrome/browser/prefs/scoped_user_pref_update.h
@@ -1,16 +1,63 @@
-// 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.
 //
 // A helper class that assists preferences in firing notifications when lists
-// are changed.
+// or dictionaries are changed.
 
 #ifndef CHROME_BROWSER_PREFS_SCOPED_USER_PREF_UPDATE_H_
 #define CHROME_BROWSER_PREFS_SCOPED_USER_PREF_UPDATE_H_
 #pragma once
 
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/scoped_ptr.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/values.h"
 #include "chrome/browser/prefs/pref_service.h"
 
+class DictionaryValue;
+class ListValue;
+class PrefService;
+
+namespace subtle {
+
+// Base class for ScopedUserPrefUpdateTemplate that contains the parts
+// that do not depend on ScopedUserPrefUpdateTemplate's template parameter.
+//
+// We need this base class mostly for making it a friend of PrefService
+// and getting access to PrefService::GetMutableUserPref and
+// PrefService::ReportUserPrefChanged.
+class ScopedUserPrefUpdateBase : public base::NonThreadSafe {
+ protected:
+  ScopedUserPrefUpdateBase(PrefService* service, const char* path);
+
+  // Calls Notify().
+  virtual ~ScopedUserPrefUpdateBase();
+
+  // Sets |value_| to |service_|->GetMutableUserPref and returns it.
+  Value* Get(Value::ValueType type);
+
+ private:
+  // If |value_| is not null, triggers a notification of PrefObservers and
+  // resets |value_|.
+  virtual void Notify();
+
+  // Weak pointer.
+  PrefService* service_;
+  // Path of the preference being updated.
+  std::string path_;
+  // Cache of value from user pref store (set between Get() and Notify() calls).
+  Value* value_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedUserPrefUpdateBase);
+};
+
+}  // namespace subtle
+
+// TODO(battre) This class is legacy and will be substituted by
+// ScopedUserPrefUpdateTemplate soon. http://crbug.com/58489
 class ScopedUserPrefUpdate {
  public:
   ScopedUserPrefUpdate(PrefService* service, const char* path);
@@ -21,4 +68,44 @@ class ScopedUserPrefUpdate {
   std::string path_;
 };
 
+// TODO(battre) Rename ScopedUserPrefUpdateTemplate to ScopedUserPrefUpdate
+// once the legacy class above is gone. http://crbug.com/58489
+
+// Class to support modifications to DictionaryValues and ListValues while
+// guaranteeing that PrefObservers are notified of changed values.
+//
+// This class may only be used on the UI thread as it requires access to the
+// PrefService.
+template <typename T, Value::ValueType type_enum_value>
+class ScopedUserPrefUpdateTemplate : public subtle::ScopedUserPrefUpdateBase {
+ public:
+  ScopedUserPrefUpdateTemplate(PrefService* service, const char* path)
+      : ScopedUserPrefUpdateBase(service, path) {}
+
+  // Triggers an update notification if Get() was called.
+  virtual ~ScopedUserPrefUpdateTemplate() {}
+
+  // Returns a mutable |T| instance that
+  // - is already in the user pref store, or
+  // - is (silently) created and written to the user pref store if none existed
+  //   before.
+  //
+  // Calling Get() implies that an update notification is necessary at
+  // destruction time.
+  //
+  // The ownership of the return value remains with the user pref store.
+  virtual T* Get() {
+    return static_cast<T*>(
+        subtle::ScopedUserPrefUpdateBase::Get(type_enum_value));
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ScopedUserPrefUpdateTemplate);
+};
+
+typedef ScopedUserPrefUpdateTemplate<DictionaryValue, Value::TYPE_DICTIONARY>
+    DictionaryPrefUpdate;
+typedef ScopedUserPrefUpdateTemplate<ListValue, Value::TYPE_LIST>
+    ListPrefUpdate;
+
 #endif  // CHROME_BROWSER_PREFS_SCOPED_USER_PREF_UPDATE_H_