Remove all ReadingList entries on managed account signout.

ios/chrome/browser/reading_list/reading_list_remover_helper.cc

+// Copyright 2017 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 "ios/chrome/browser/reading_list/reading_list_remover_helper.h"
+
+#include "components/reading_list/ios/reading_list_model.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+#include "ios/chrome/browser/reading_list/reading_list_download_service.h"
+#include "ios/chrome/browser/reading_list/reading_list_download_service_factory.h"
+#include "ios/chrome/browser/reading_list/reading_list_model_factory.h"
+
+namespace reading_list {
+
+ReadingListRemoverHelper::ReadingListRemoverHelper(
+    ios::ChromeBrowserState* browser_state)
+    : ReadingListModelObserver(), scoped_observer_(this) {
+  reading_list_model_ =
+      ReadingListModelFactory::GetForBrowserState(browser_state);
+  reading_list_download_service_ =
+      ReadingListDownloadServiceFactory::GetForBrowserState(browser_state);
+}
+
+ReadingListRemoverHelper::~ReadingListRemoverHelper() {}
+
+void ReadingListRemoverHelper::ReadingListModelLoaded(
+    const ReadingListModel* model) {
+  scoped_observer_.Remove(reading_list_model_);
+
+  bool model_cleared = reading_list_model_->DeleteAllEntries();
+  reading_list_download_service_->Clear();
+  reading_list_model_ = nullptr;
+  if (completion_) {
+    // |completion_| may delete this. Do not use the object after this call.
+    std::move(completion_).Run(model_cleared);
+  }
+}
+
+void ReadingListRemoverHelper::ReadingListModelBeingDeleted(
+    const ReadingListModel* model) {
+  scoped_observer_.Remove(reading_list_model_);
+  reading_list_model_ = nullptr;
+  if (completion_) {
+    // |completion_| may delete this. Do not use the object after this call.
+    std::move(completion_).Run(false);
+  }
+}
+
+void ReadingListRemoverHelper::RemoveAllUserReadingListItemsIOS(
+    Callback completion) {
+  if (!reading_list_model_) {
+    std::move(completion_).Run(false);

[sdefresne, 2017/03/20 15:09:40]

Maybe add the following comment here too:

  // |completion_| may delete this. Do not use the object after this call.

[Olivier, 2017/03/21 10:10:15]

Done.

+    return;
+  }
+  completion_ = std::move(completion);
+
+  // Calls ReadingListModelLoaded if model is already loaded.
+  scoped_observer_.Add(reading_list_model_);
+}
+
+}  // namespace reading_list