[GCM] API update to allow only a single sender in registration

google_apis/gcm/engine/registration_request.h

Index: google_apis/gcm/engine/registration_request.h
diff --git a/google_apis/gcm/engine/registration_request.h b/google_apis/gcm/engine/registration_request.h
index c5aff57fbafec2e1e565d7c7e28e8fa2d3315e73..8247dc07730f4657689287879ec03a84208cb842 100644
--- a/google_apis/gcm/engine/registration_request.h
+++ b/google_apis/gcm/engine/registration_request.h
@@ -63,7 +63,7 @@ class GCM_EXPORT RegistrationRequest : public net::URLFetcherDelegate {
                 uint64 security_token,
                 const std::string& app_id,
                 const std::string& cert,
-                const std::vector<std::string>& sender_ids);
+                const std::string& sender_id);
     ~RequestInfo();
 
     // Android ID of the device.
@@ -74,8 +74,8 @@ class GCM_EXPORT RegistrationRequest : public net::URLFetcherDelegate {
     std::string app_id;
     // Certificate of the application.
     std::string cert;
-    // List of IDs of senders. Allowed up to 100.
-    std::vector<std::string> sender_ids;
+    // A sender ID the registration is for.
+    std::string sender_id;
   };
 
   RegistrationRequest(