Add badge to web notifications.

content/common/notification_constants.h

Index: content/common/notification_constants.h
diff --git a/content/common/notification_constants.h b/content/common/notification_constants.h
index 5c4a1eba671ae4f5822d15c283148c99d8968f91..2573a6eb8f8c76c6947609741d11e4b322bad515 100644
--- a/content/common/notification_constants.h
+++ b/content/common/notification_constants.h
@@ -16,6 +16,10 @@ static const size_t kPlatformNotificationMaxActions = 2;
 // 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