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

components/gcm_driver/gcm_account_mapper.cc

Index: components/gcm_driver/gcm_account_mapper.cc
diff --git a/components/gcm_driver/gcm_account_mapper.cc b/components/gcm_driver/gcm_account_mapper.cc
index 02ba9f1ab596ac074c83546b66bad26bffb986c2..e1b4f9221cb55a65ed659081546676208eadc7af 100644
--- a/components/gcm_driver/gcm_account_mapper.cc
+++ b/components/gcm_driver/gcm_account_mapper.cc
@@ -11,6 +11,7 @@
 #include "base/time/clock.h"
 #include "base/time/default_clock.h"
 #include "components/gcm_driver/gcm_driver_desktop.h"
+#include "components/gcm_driver/gcm_message_status.h"
 #include "google_apis/gcm/engine/gcm_store.h"
 
 namespace gcm {
@@ -39,6 +40,8 @@ std::string GenerateMessageID() {
   return base::GenerateGUID();
 }
 
+void NullReceiptCallback(GCMMessageStatus status) {}
+
 }  // namespace
 
 const char kGCMAccountMapperAppId[] = "com.google.android.gms";
@@ -181,7 +184,10 @@ void GCMAccountMapper::OnMessage(const std::string& app_id,
   // Ensuring the message does not carry the embedded app ID.
   IncomingMessage new_message = message;
   new_message.data.erase(new_message.data.find(kGCMSendToGaiaIdAppIdKey));
-  dispatch_message_callback_.Run(embedded_app_id, new_message);
+  // TODO(harkness): Update this to use a real callback once callbacks are
+  // plumbed to all GCMAppHandlers.
+  dispatch_message_callback_.Run(embedded_app_id, new_message,
+                                 base::Bind(&NullReceiptCallback));
 }
 
 void GCMAccountMapper::OnMessagesDeleted(const std::string& app_id) {