Include time elapsed since start of a remoting session in each log entry.

remoting/webapp/crd/js/log_to_server.js

 // Copyright (c) 2012 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.
 
 /**
  * @fileoverview
  * Module for sending log entries to the server.
  */
 
 'use strict';
@@ skipping 48 matching lines @@
  */
 remoting.LogToServer.prototype.logClientSessionStateChange =
     function(state, connectionError) {
   this.maybeExpireSessionId_();
   // Set the session start time if we haven't done so already.
   if (remoting.LogToServer.isStartOfSession_(state)) {
     if (this.sessionStartTime_ == 0) {
       this.sessionStartTime_ = new Date().getTime();
     }
   }
+  var elapsedTimeInMs = new Date().getTime() - this.sessionStartTime_;
+
   // Log the session state change.
   var entry = remoting.ServerLogEntry.makeClientSessionStateChange(
       state, connectionError, this.mode_);
   entry.addHostFields();
   entry.addChromeVersionField();
   entry.addWebappVersionField();
   entry.addSessionIdField(this.sessionId_);
   // Maybe clear the session start time, and log the session duration.
   if (remoting.LogToServer.shouldAddDuration_(state) &&
       (this.sessionStartTime_ != 0)) {
     entry.addSessionDurationField(
         (new Date().getTime() - this.sessionStartTime_) / 1000.0);
     if (remoting.LogToServer.isEndOfSession_(state)) {
       this.sessionStartTime_ = 0;
     }
   }
+
+  // Log the time taken to get to this state from the time this session started.
+  entry.addElapsedTimeMs(elapsedTimeInMs);

[Jamie, 2015/02/27 02:24:46]

This is still only being added for session state change events. We need it for
signal strategy events at least, and I think there's value in having it for all
events. I haven't looked in detail, but I think you'll need to add it to the
log_() method, and look into how the session start time is set. You need to make
sure it's set before the first log message is sent, but if the LogToServer
instance is re-used between connections, you'll also need to reset it--it's
probably better to make sure the LogToServer is not re-used.

[anandc, 2015/02/27 21:49:29]

Done.

LogToServer is reset at the start of each session. See:
https://code.google.com/p/chromium/codesearch#chromium/src/remoting/webapp/cr...

Session start time is being set when we first get a "Connecting" event. See line
65 above.

The first call to log_ is made right after the first "Connecting" event. I
confirmed this by checking values in the console debugger. 

Based on all that, adding the elapsed-time field within log_ now.

   this.log_(entry);
   // Don't accumulate connection statistics across state changes.
   this.logAccumulatedStatistics_();
   this.statsAccumulator_.empty();
   // Maybe clear the session ID.
   if (remoting.LogToServer.isEndOfSession_(state)) {
     this.clearSessionId_();
   }
 };
 
 /**
  * Set the connection type (direct, stun relay).
  *
  * @param {string} connectionType
  */
 remoting.LogToServer.prototype.setConnectionType = function(connectionType) {
   this.connectionType_ = connectionType;
 };
 
 /**
  * @param {remoting.SignalStrategy.Type} strategyType
  * @param {remoting.FallbackSignalStrategy.Progress} progress
- * @param {number} elapsedTimeInMs
  */
 remoting.LogToServer.prototype.logSignalStrategyProgress =
-    function(strategyType, progress, elapsedTimeInMs) {
+    function(strategyType, progress) {
   this.maybeExpireSessionId_();
   var entry = remoting.ServerLogEntry.makeSignalStrategyProgress(
-      this.sessionId_, strategyType, progress, elapsedTimeInMs);
+      this.sessionId_, strategyType, progress);
   this.log_(entry);
 };
 
 /**
  * Whether a session state is one of the states that occurs at the start of
  * a session.
  *
  * @private
  * @param {remoting.ClientSession.State} state
  * @return {boolean}
@@ skipping 146 matching lines @@
 remoting.LogToServer.generateSessionId_ = function() {
   var idArray = [];
   for (var i = 0; i < remoting.LogToServer.SESSION_ID_LEN_; i++) {
     var index =
         Math.random() * remoting.LogToServer.SESSION_ID_ALPHABET_.length;
     idArray.push(
         remoting.LogToServer.SESSION_ID_ALPHABET_.slice(index, index + 1));
   }
   return idArray.join('');
 };