Cast: Avoid hitting a DCHECK caused by race condition

media/cast/net/rtcp/rtcp.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/cast/net/rtcp/rtcp.h"
 
 #include "media/cast/cast_config.h"
 #include "media/cast/cast_defines.h"
 #include "media/cast/cast_environment.h"
 #include "media/cast/net/cast_transport_defines.h"
@@ skipping 141 matching lines @@
       rtp_receiver_statistics->GetStatistics(
           &report_block.fraction_lost, &report_block.cumulative_lost,
           &report_block.extended_high_sequence_number, &report_block.jitter);
     }
 
     report_block.last_sr = last_report_truncated_ntp_;
     if (!time_last_report_received_.is_null()) {
       uint32 delay_seconds = 0;
       uint32 delay_fraction = 0;
       base::TimeDelta delta = now - time_last_report_received_;
-
-      // TODO(hclam): DLRR is not used by any receiver. Consider removing
-      // it. There is one race condition in the computation of the time for
-      // DLRR: current time is submitted to this method while
-      // |time_last_report_received_| is updated just before that. This can
-      // happen if current time is not submitted synchronously.
-      if (delta < base::TimeDelta())
-        delta = base::TimeDelta();
       ConvertTimeToFractions(delta.InMicroseconds(), &delay_seconds,
                              &delay_fraction);
       report_block.delay_since_last_sr =
           ConvertToNtpDiff(delay_seconds, delay_fraction);
     } else {
       report_block.delay_since_last_sr = 0;
     }
   }
   rtcp_sender_->SendRtcpFromRtpReceiver(packet_type_flags,
                                         &report_block,
@@ skipping 15 matching lines @@
   SaveLastSentNtpTime(current_time, current_ntp_seconds,
                       current_ntp_fractions);
 
   RtcpDlrrReportBlock dlrr;
   if (!time_last_report_received_.is_null()) {
     packet_type_flags |= kRtcpDlrr;
     dlrr.last_rr = last_report_truncated_ntp_;
     uint32 delay_seconds = 0;
     uint32 delay_fraction = 0;
     base::TimeDelta delta = current_time - time_last_report_received_;
+    // TODO(hclam): DLRR is not used by any receiver. Consider removing
+    // it. There is one race condition in the computation of the time for
+    // DLRR: current time is submitted to this method while
+    // |time_last_report_received_| is updated just before that. This can
+    // happen if current time is not submitted synchronously.
+    if (delta < base::TimeDelta())
+      delta = base::TimeDelta();
     ConvertTimeToFractions(delta.InMicroseconds(), &delay_seconds,
                            &delay_fraction);
 
     dlrr.delay_since_last_rr = ConvertToNtpDiff(delay_seconds, delay_fraction);
   }
 
   RtcpSenderInfo sender_info;
   sender_info.ntp_seconds = current_ntp_seconds;
   sender_info.ntp_fraction = current_ntp_fractions;
   sender_info.rtp_timestamp = current_time_as_rtp_timestamp;
@@ skipping 145 matching lines @@
 }
 
 void Rtcp::OnReceivedReceiverLog(const RtcpReceiverLogMessage& receiver_log) {
   if (log_callback_.is_null())
     return;
   log_callback_.Run(receiver_log);
 }
 
 }  // namespace cast
 }  // namespace media