Upstream Chrome on iOS source code [9/11].

ios/chrome/browser/ui/toolbar/tools_menu_button_observer_bridge.mm

+// Copyright 2016 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.
+
+#import "ios/chrome/browser/ui/toolbar/tools_menu_button_observer_bridge.h"
+
+#include "components/reading_list/ios/reading_list_model.h"
+#import "ios/chrome/browser/ui/toolbar/toolbar_tools_menu_button.h"
+
+ToolsMenuButtonObserverBridge::ToolsMenuButtonObserverBridge(
+    ReadingListModel* readingListModel,
+    ToolbarToolsMenuButton* button)
+    : readingListModel_(readingListModel), button_([button retain]) {
+  readingListModel_->AddObserver(this);
+};
+
+ToolsMenuButtonObserverBridge::~ToolsMenuButtonObserverBridge() {
+  readingListModel_->RemoveObserver(this);
+}
+
+void ToolsMenuButtonObserverBridge::ReadingListModelLoaded(
+    const ReadingListModel* model) {
+  UpdateButtonWithModel(model);
+}
+void ToolsMenuButtonObserverBridge::ReadingListDidApplyChanges(
+    ReadingListModel* model) {
+  UpdateButtonWithModel(model);
+}
+
+void ToolsMenuButtonObserverBridge::UpdateButtonWithModel(
+    const ReadingListModel* model) {
+  bool readingListContainsUnreadItems = model->unread_size() > 0;
+  [button_ setReadingListContainsUnreadItems:readingListContainsUnreadItems];
+}