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

chrome/browser/gcm/fake_gcm_profile_service.h

Index: chrome/browser/gcm/fake_gcm_profile_service.h
diff --git a/chrome/browser/gcm/fake_gcm_profile_service.h b/chrome/browser/gcm/fake_gcm_profile_service.h
index 2a5ab46a17c23b6f29a236ca95c380a954292c71..bc65590636b8edf4d07fe3767fa5e84ad53f3d58 100644
--- a/chrome/browser/gcm/fake_gcm_profile_service.h
+++ b/chrome/browser/gcm/fake_gcm_profile_service.h
@@ -35,7 +35,8 @@ class FakeGCMProfileService : public GCMProfileService {
   void AddExpectedUnregisterResponse(GCMClient::Result result);
 
   void DispatchMessage(const std::string& app_id,
-                       const IncomingMessage& message);
+                       const IncomingMessage& message,
+                       const MessageReceiptCallback& optional_receipt_callback);
 
   const OutgoingMessage& last_sent_message() const {
     return last_sent_message_;