Add the NotificationDatabaseData structure and protobuf

content/browser/notifications/notification_proto.gyp

Index: content/browser/notifications/notification_proto.gyp
diff --git a/content/browser/notifications/notification_proto.gyp b/content/browser/notifications/notification_proto.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..effe03e10fb1a8b004b285f5e98ac1df4a5137d2
--- /dev/null
+++ b/content/browser/notifications/notification_proto.gyp
@@ -0,0 +1,17 @@
+{
+  'targets': [
+    {
+      # GN version: //content/browser/notifications:notification_proto
+      'target_name': 'notification_proto',
+      'type': 'static_library',
+      'sources': [
+        'notification_database_data.proto',
+      ],
+      'variables': {
+        'proto_in_dir': '.',
+        'proto_out_dir': 'content/browser/notifications',
+      },
+      'includes': [ '../../../build/protoc.gypi' ]
+    },
+  ],
+}