Battery Status API: add UMA logging for Linux.

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 5f84acab589b5a01833a077269d67b967a632eef..0d23caff028cada42b9553b40a9f20da708ecad0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1927,6 +1927,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="BatteryStatus.NumberBatteriesLinux"
+    enum="BatteryStatusNumberBatteriesLinux">
+  <owner>timvolodine@chromium.org</owner>
+  <summary>
+    Number of batteries reported by the UPower service on Linux at the start of
+    the Battery Status API.
+  </summary>
+</histogram>
+
 <histogram name="BatteryStatus.StartAndroid" enum="BooleanSuccess">
   <owner>timvolodine@chromium.org</owner>
   <summary>
@@ -37671,6 +37680,10 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="2" label="Bad"/>
 </enum>
 
+<enum name="BatteryStatusNumberBatteriesLinux" type="int">
+  <int value="5" label="5+"/>
+</enum>
+
 <enum name="BlacklistSetup" type="int">
   <int value="0" label="Blacklist enabled"/>
   <int value="1" label="Blacklist ran successfully."/>