Added UMA metrics for ChromeOS first-run UI.

chrome/browser/chromeos/first_run/first_run.cc

Index: chrome/browser/chromeos/first_run/first_run.cc
diff --git a/chrome/browser/chromeos/first_run/first_run.cc b/chrome/browser/chromeos/first_run/first_run.cc
index 90b132246b159ba16de28819bb322d12cd637a01..20d2db8aab0635d6429ff9fdf7f7affa3489086a 100644
--- a/chrome/browser/chromeos/first_run/first_run.cc
+++ b/chrome/browser/chromeos/first_run/first_run.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/command_line.h"
+#include "base/metrics/histogram.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/first_run/first_run_controller.h"
 #include "chrome/browser/chromeos/login/user_manager.h"
@@ -101,6 +102,7 @@ void MaybeLaunchDialogAfterSessionStart() {
 }
 
 void LaunchTutorial() {
+  UMA_HISTOGRAM_COUNTS("CrosFirstRun.TutorialLaunched", 1);

[Alexei Svitkine (slow), 2014/01/15 16:02:38]

This should probably be UMA_HISTOGRAM_BOOLEAN or alternatively, it should be
grouped with some other enum histograms, to make things easier to compare.

[dzhioev (left Google), 2014/01/15 22:12:54]

It's intended to count how many times tutorial was launched. Formally it is
histogram with only one value - 1. I didn't find other way to count events
except for RecordAction("SOMETHING"). But stats for events recorded by
RecordAction are saved only for 7 days. 

[Alexei Svitkine (slow), 2014/01/15 22:21:36]

UMA_HISTOGRAM_BOOLEAN() should do what you want here - it will sum up the number
of times its hit in the dashboards. In fact, it should be equivalent (but more
efficient at runtime in memory use).

[dzhioev (left Google), 2014/01/16 13:21:14]

Done.

   FirstRunController::Start();
 }