Battery Status API: add UMA logging for Windows.

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 e225050bcaa860786c5c188d42f6de4ebb4f4f8f..7621e53c4cb8a4122a08d82f97f3377b8902623c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1970,6 +1970,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="BatteryStatus.NumberBatteriesWin"
+    enum="BatteryStatusNumberBatteriesWin">
+  <owner>timvolodine@chromium.org</owner>
+  <summary>
+    Number of batteries reported by Windows at the start of the Battery Status
+    API.
+  </summary>
+</histogram>
+
 <histogram name="BatteryStatus.StartAndroid" enum="BooleanSuccess">
   <owner>timvolodine@chromium.org</owner>
   <summary>
@@ -38715,6 +38724,12 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="5" label="5+"/>
 </enum>
 
+<enum name="BatteryStatusNumberBatteriesWin" type="int">
+  <int value="0" label="Unknown"/>
+  <int value="1" label="0"/>
+  <int value="2" label="1+"/>
+</enum>
+
 <enum name="BlacklistSetup" type="int">
   <int value="0" label="Blacklist enabled"/>
   <int value="1" label="Blacklist ran successfully."/>