Add badge to web notifications.

content/common/notification_constants.h

 // Copyright 2015 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.
 
 #ifndef CONTENT_COMMON_NOTIFICATION_CONSTANTS_H_
 #define CONTENT_COMMON_NOTIFICATION_CONSTANTS_H_
 
 #include <stddef.h>
 
 namespace content {
 
 // Maximum number of actions on a Platform Notification.
 static const size_t kPlatformNotificationMaxActions = 2;
 
 // The maximum reasonable notification icon size, scaled from dip units to
 // pixels using the largest supported scaling factor.
 static const int kPlatformNotificationMaxIconSizePx = 320;  // 80 dip * 4
 
+// The maximum reasonable badge size, scaled from dip units to pixels using the
+// largest supported scaling factor.
+static const int kPlatformNotificationMaxBadgeSizePx = 96;  // 24 dip * 4
+
 // The maximum reasonable action icon size, scaled from dip units to
 // pixels using the largest supported scaling factor.
 static const int kPlatformNotificationMaxActionIconSizePx = 128;  // 32 dip * 4
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_NOTIFICATION_CONSTANTS_H_