[Sync] Rip out overly-complicated ExtensionData class

chrome/browser/extensions/extension_sync_data.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_sync_data.h"
 
+#include "base/logging.h"
+
 ExtensionSyncData::ExtensionSyncData()
     : uninstalled(false), enabled(false), incognito_enabled(false) {}
 
 ExtensionSyncData::~ExtensionSyncData() {}
+
+void ExtensionSyncData::Merge(const ExtensionSyncData& new_data) {
+  CHECK_EQ(id, new_data.id);
+  CHECK(!uninstalled);
+  CHECK(!new_data.uninstalled);
+
+  // Copy version-independent properties.
+  enabled = new_data.enabled;
+  incognito_enabled = new_data.incognito_enabled;
+
+  // Copy version-dependent properties if version <= new_data.version.
+  if (version.CompareTo(new_data.version) <= 0) {
+    version = new_data.version;
+    update_url = new_data.update_url;
+    name = new_data.name;
+  }
+}