Add support for uninstalling components and use it in SupervisedUserWhitelistInstaller.

components/update_client/update_client.cc

 // Copyright 2014 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 "components/update_client/update_client.h"
 
 #include "components/update_client/crx_update_item.h"
 
 namespace update_client {
 
 CrxUpdateItem::CrxUpdateItem()
     : status(kNew),
+      unregistered(false),
       on_demand(false),
       diff_update_failed(false),
       error_category(0),
       error_code(0),
       extra_code1(0),
       diff_error_category(0),
       diff_error_code(0),
       diff_extra_code1(0) {
 }
 
 CrxUpdateItem::~CrxUpdateItem() {
 }
 
-CrxComponent::CrxComponent()
-    : installer(NULL), allow_background_download(true) {
+CrxComponent::CrxComponent() : allow_background_download(true) {
 }
 
 CrxComponent::~CrxComponent() {
 }
 
 }  // namespace update_client