Implement the Notification `timestamp` property

content/browser/notifications/notification_database_data.proto

Index: content/browser/notifications/notification_database_data.proto
diff --git a/content/browser/notifications/notification_database_data.proto b/content/browser/notifications/notification_database_data.proto
index 3047d2b4356e28c5b79410ad156eb755fd97687b..03d8172cf87b50aaa4e1cf463c04ee77f7339949 100644
--- a/content/browser/notifications/notification_database_data.proto
+++ b/content/browser/notifications/notification_database_data.proto
@@ -29,7 +29,7 @@ message NotificationDatabaseDataProto {
   // Actual data payload of the notification. This message is the protocol
   // buffer meant to serialize the content::PlatformNotificationData structure.
   //
-  // Next tag: 12
+  // Next tag: 13
   message NotificationData {
     enum Direction {
       LEFT_TO_RIGHT = 0;
@@ -44,6 +44,7 @@ message NotificationDatabaseDataProto {
     optional string tag = 5;
     optional string icon = 6;
     repeated int32 vibration_pattern = 9 [packed=true];
+    optional double timestamp = 12;

[johnme, 2015/10/20 17:12:21]

Why not an int64, to match the base::Time in PlatformNotificationData? You can
use ToInternalValue/FromInternalValue to serialize/deserialize.

(the double you get from ToDoubleT is in microseconds, so it's not consistent
with the Blink one either)

[Peter Beverloo, 2016/01/28 17:18:29]

Done.

     optional bool silent = 7;
     optional bool require_interaction = 11;
     optional bytes data = 8;