Add command line overrides for GCM checkin URL & MCS endpoint

google_apis/gcm/engine/gservices_settings.h

Index: google_apis/gcm/engine/gservices_settings.h
diff --git a/google_apis/gcm/engine/gservices_settings.h b/google_apis/gcm/engine/gservices_settings.h
index d3aeeb03d29511da2c5475be9817ea1f6204ff15..7811f9e38bd8d02af1d2821d25c827fa11ac0824 100644
--- a/google_apis/gcm/engine/gservices_settings.h
+++ b/google_apis/gcm/engine/gservices_settings.h
@@ -26,9 +26,6 @@ class GCM_EXPORT GServicesSettings {
   // Minimum periodic checkin interval in seconds.
   static const base::TimeDelta MinimumCheckinInterval();
 
-  // Default checkin URL.
-  static const GURL DefaultCheckinURL();
-
   // Calculates digest of provided settings.
   static std::string CalculateDigest(const SettingsMap& settings);
 
@@ -56,7 +53,7 @@ class GCM_EXPORT GServicesSettings {
   // Gets address of main MCS endpoint.
   GURL GetMCSMainEndpoint() const;
 
-  // Gets address of fallback MCS endpoint.
+  // Gets address of fallback MCS endpoint. Will be empty if there isn't one.
   GURL GetMCSFallbackEndpoint() const;
 
   // Gets the URL to use when registering or unregistering the apps.