Add onChanged events to the extension settings API, both from sync and between

chrome/browser/extensions/extension_settings_changes.cc

+// 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.
+
+#include "chrome/browser/extensions/extension_settings_changes.h"
+
+#include "base/json/json_writer.h"
+
+ExtensionSettingsChanges::ExtensionSettingsChanges() : inner_(new Inner()) {}
+
+ExtensionSettingsChanges::~ExtensionSettingsChanges() {}
+
+void ExtensionSettingsChanges::AppendChange(
+    const std::string& key, Value* old_value, Value* new_value) {
+  DictionaryValue* change = new DictionaryValue();
+  change->Set("key", Value::CreateStringValue(key));

[akalin, 2011/10/14 10:31:49]

can do SetString()

[not at google - send to devlin, 2011/10/17 00:04:33]

Done.

+  if (old_value) {
+    change->Set("oldValue", old_value);
+  }
+  if (new_value) {
+    change->Set("newValue", new_value);
+  }
+  inner_->changes.Append(change);
+}
+
+std::string ExtensionSettingsChanges::ToJson() const {
+  std::string event_json;
+  base::JSONWriter::Write(&inner_->changes, false, &event_json);
+  return event_json;
+}