Provide a mechanism for the GCM driver to send message receipts to GCM.

components/gcm_driver/gcm_driver_android.cc

Index: components/gcm_driver/gcm_driver_android.cc
diff --git a/components/gcm_driver/gcm_driver_android.cc b/components/gcm_driver/gcm_driver_android.cc
index a512e8248d9a045c091c9c2440ec80577d1b26d8..47b926fe7b0088159148ed4ca0c78dfd122f95fc 100644
--- a/components/gcm_driver/gcm_driver_android.cc
+++ b/components/gcm_driver/gcm_driver_android.cc
@@ -109,7 +109,16 @@ void GCMDriverAndroid::OnMessageReceived(
   recorder_.RecordDataMessageReceived(app_id, message.sender_id,
                                       message_byte_size);
 
-  DispatchMessage(app_id, message);
+  DispatchMessage(app_id, message,
+                  base::Bind(&GCMDriverAndroid::SendMessageReceipt,

[Peter Beverloo, 2017/01/13 01:46:12]

Why isn't this BindToCurrentThread? If we're telling AppHandlers that it's OK to
invoke the callback on any thread, we need to be consistent about that.

[harkness, 2017/01/19 13:20:42]

Done.

+                             weak_ptr_factory_.GetWeakPtr(), app_id, ""));

[Peter Beverloo, 2017/01/13 01:46:12]

Why the empty string for |message_id|? Can we just not pass it until it's
available?

[harkness, 2017/01/19 13:20:42]

Sure, that's a good idea. Done.

+}
+
+void GCMDriverAndroid::SendMessageReceipt(const std::string& app_id,
+                                          const std::string& message_id,
+                                          GCMMessageStatus status) {
+  // TODO(harkness) Implement message receipts in android.

[Peter Beverloo, 2017/01/13 01:46:12]

nit: please mention a bug

[harkness, 2017/01/19 13:20:42]

Done.

+  NOTIMPLEMENTED();
 }
 
 // static