[GCM] Add TTL support

google_apis/gcm/base/mcs_util.h

Index: google_apis/gcm/base/mcs_util.h
diff --git a/google_apis/gcm/base/mcs_util.h b/google_apis/gcm/base/mcs_util.h
index 7f92564ad27fc4d47f1af91a4382a7dfa0816920..a983e1562f437787f6c13c6f45eb0636d51c49f3 100644
--- a/google_apis/gcm/base/mcs_util.h
+++ b/google_apis/gcm/base/mcs_util.h
@@ -15,6 +15,10 @@
 #include "google_apis/gcm/base/gcm_export.h"
 #include "google_apis/gcm/protocol/mcs.pb.h"
 
+namespace base {
+class Clock;
+}
+
 namespace net {
 class StreamSocket;
 }
@@ -76,6 +80,13 @@ GCM_EXPORT void SetLastStreamIdReceived(
     uint32 last_stream_id_received,
     google::protobuf::MessageLite* protobuf);
 
+// Returns whether the TTL (time to live) for this message has expired, based
+// on the |sent| timestamps and base::TimeTicks::Now(). If |protobuf| is not
+// for a DataMessageStanza or the TTL is 0, will return false.
+GCM_EXPORT bool HasTTLExpired(const google::protobuf::MessageLite& protobuf,
+                              base::Clock* clock);
+GCM_EXPORT int GetTTL(const google::protobuf::MessageLite& protobuf);
+
 }  // namespace gcm
 
 #endif  // GOOGLE_APIS_GCM_BASE_MCS_UTIL_H_