Add UMA stats for Chromoting connection details.

remoting/webapp/base/js/client_session.js

Index: remoting/webapp/base/js/client_session.js
diff --git a/remoting/webapp/base/js/client_session.js b/remoting/webapp/base/js/client_session.js
index 329decea3d212eefa74c3b3093d4bd65f85df4c4..d0087438656d7f703b1d3c66264525b0d14922c6 100644
--- a/remoting/webapp/base/js/client_session.js
+++ b/remoting/webapp/base/js/client_session.js
@@ -566,11 +566,31 @@ remoting.ClientSession.prototype.setState_ = function(newState) {
   }
 
   this.notifyStateChanges_(oldState, this.state_);
+  if (this.state_ > 1) {

[kelvinp, 2015/08/21 16:29:23]

Currently initializing doesn't fire so this check is not necessary.
And if we ended up firing initializing one day, don't we want to upload that to
UMA as well?

[anandc, 2015/08/21 18:56:56]

Done.

+    // Record state in an UMA histogram if it is after initializing.
+    recordState(this.state_);
+  }
   this.logger_.logClientSessionStateChange(
       this.state_, this.error_, this.xmppErrorCache_.getFirstError());
 };
 
 /**
+ * Records a Chromoting Connection State.
+ * @param {remoting.ClientSession.State} state State identifier.
+ */
+function recordState(state) {
+  var metricDescription = {
+    metricName: 'Chromoting.Connections',
+    type: 'histogram-linear',
+    min: 2,

[kelvinp, 2015/08/21 16:29:24]

Use enum values from remoting.ClientSession.State

[anandc, 2015/08/21 18:56:56]

Done.

+    max: 7,

[kelvinp, 2015/08/21 16:29:23]

The enum range is not consecutive, for example CONNECTION_CANCELED is -3 and
FAILED is 6

[anandc, 2015/08/21 18:56:56]

Thanks. PTAL at the latest implementation.
I considered what you mentioned offline about checking for the value of each
state and calling the corresponding enum for recordValue. However, this does not
fix the problem of keeping the 2 lists, the one here and the other in
histograms.xml in sync. So going with what seems to be a cleaner implementation.

+    buckets: 7

[anandc, 2015/08/21 16:23:01]

We only want to log when the connection state is after Initializing. So min is
2. The max expected value is 6, and histograms should be defined with the max to
be 1 above the expected value. And # of buckets should 1 above the total
distinct values to account for overflow.
I'll add these comments to the code later. Just sending this out for review now.
LMK if any of these are incorrect.

+  };
+
+  chrome.metricsPrivate.recordValue(metricDescription, state);
+}
+
+/**
  * @param {remoting.ClientSession.State} oldState The new state for the session.
  * @param {remoting.ClientSession.State} newState The new state for the session.
  * @private