Ensure the xpc transaction is ended

chrome/browser/ui/cocoa/notifications/xpc_transaction_handler.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 <AppKit/AppKit.h>
+#import <Foundation/Foundation.h>
+
+#import "chrome/browser/ui/cocoa/notifications/xpc_transaction_handler.h"
+
+@class NSUserNotificationCenter;
+
+@implementation XPCTransactionHandler {
+  bool transactionOpen_;
+}
+
+- (instancetype)init {
+  if ((self = [super init])) {
+    transactionOpen_ = false;
+  }
+  return self;
+}
+
+- (void)openTransactionIfNeeded {
+  @synchronized(self) {
+    if (transactionOpen_) {
+      return;
+    }
+    xpc_transaction_begin();
+    transactionOpen_ = true;
+  }
+}
+
+- (void)closeTransactionIfNeeded {
+  @synchronized(self) {
+    NSUserNotificationCenter* notificationCenter =
+        [NSUserNotificationCenter defaultUserNotificationCenter];
+    NSUInteger showing = [[notificationCenter deliveredNotifications] count];
+    if (showing == 0) {
+      xpc_transaction_end();
+      transactionOpen_ = false;
+    }
+  }
+}
+@end