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

components/gcm_driver/gcm_driver_android.h

Index: components/gcm_driver/gcm_driver_android.h
diff --git a/components/gcm_driver/gcm_driver_android.h b/components/gcm_driver/gcm_driver_android.h
index ab5c9f3700aa1087c515270b70c4052e6c31856e..e51f4f3714c3b974ecbff4fe93c1d2cc8a33b4a9 100644
--- a/components/gcm_driver/gcm_driver_android.h
+++ b/components/gcm_driver/gcm_driver_android.h
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "components/gcm_driver/gcm_driver.h"
+#include "components/gcm_driver/gcm_message_status.h"
 #include "components/gcm_driver/gcm_stats_recorder_android.h"
 
 namespace base {
@@ -97,6 +98,10 @@ class GCMDriverAndroid : public GCMDriver,
       override;
 
  private:
+  void SendMessageReceipt(const std::string& app_id,
+                          const std::string& message_id,
+                          GCMMessageStatus status);
+
   base::android::ScopedJavaGlobalRef<jobject> java_ref_;
 
   // Callback for GetGCMStatistics.