Chromoting to report roundtrip latency

remoting/client/chromoting_client.cc

Index: remoting/client/chromoting_client.cc
diff --git a/remoting/client/chromoting_client.cc b/remoting/client/chromoting_client.cc
index 2e599f121d1a8bbf1ff971c0b162f3246388301d..0c4549526f8d47e38350e6fa3e3da800a19da1de 100644
--- a/remoting/client/chromoting_client.cc
+++ b/remoting/client/chromoting_client.cc
@@ -137,6 +137,13 @@ void ChromotingClient::ProcessVideoPacket(const VideoPacket* packet,
     stats_.video_capture_ms()->Record(packet->capture_time_ms());
   if (packet->has_encode_time_ms())
     stats_.video_encode_ms()->Record(packet->encode_time_ms());
+  if (packet->has_client_sequence_number() &&
+      packet->client_sequence_number()) {

[Wez, 2011/04/05 13:46:20]

Checking for presence of client_sequence_number is for backwards compatibility
with older Hosts.
Checking for non-zero value is because zero means that the Host has already sent
us a VideoPacket corresponding to the most recent input event.
This isn't clear without looking at the ScreenRecorder implementation, though.

It would be better to have the client keep a record of the most-recent sequence
number it received a VideoPacket for, and only log the round-trip if it receives
one with a higher sequence number, I think.

If you'd prefer to keep the arrangement where the Host zeroes its internal idea
of the client_sequence_number then better to have that propagate to the client
as an absence of a client_sequence_number field at all, and to clarify in this
the proto that zero is not a valid sequence number for a client to send.

[Alpha Left Google, 2011/04/08 00:07:20]

Sounds good to me. The reason I didn't want to not put client_sequence_number is
because I needed to add two places in two different encoder. Your scheme seems
better.

+    base::TimeDelta round_trip_latency =
+        base::Time::Now() -
+        base::Time::FromInternalValue(packet->client_sequence_number());
+    stats_.round_trip_ms()->Record(round_trip_latency.InMilliseconds());
+  }
 
   received_packets_.push_back(QueuedVideoPacket(packet, done));
   if (!packet_being_processed_)