[Merge M48] Add Startup.SystemUptime histogram.

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index b926d666bbd679253b3c4191c16c9834c16cb71c..75fd853495714895fc3dab0d87b48dbdb4e05eed 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -45782,6 +45782,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Startup.SystemUptime" units="milliseconds">
+  <owner>fdoray@chromium.org</owner>
+  <summary>
+    The time elapsed between system boot and Chrome browser process launch. This
+    is recorded just before the main message loop starts.
+  </summary>
+</histogram>
+
 <histogram name="Startup.Temperature" enum="StartupTemperature">
   <owner>chrisha@chromium.org</owner>
   <summary>
@@ -82281,6 +82289,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Startup.LoadTime.ExeMainToDllMain"/>
   <affected-histogram name="Startup.LoadTime.ProcessCreateToDllMain"/>
   <affected-histogram name="Startup.LoadTime.ProcessCreateToExeMain"/>
+  <affected-histogram name="Startup.SystemUptime"/>
 </histogram_suffixes>
 
 <histogram_suffixes name="StartupTimeBombAlarm" separator=".">