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 57cf2870374239a36267d9e56c954da44c72c716..2dd7578e6ab4948ed0cfbc6a8f20ef0c15ab4532 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1945,6 +1945,15 @@ 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>
@@ -38083,6 +38092,11 @@ 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="1" label="1+"/>
+  <int value="2" label="Unknown"/>

[Ilya Sherman, 2014/09/12 19:32:58]

nit: It's often best to put the "Unknown" bucket first, in case you're able to
improve your code to distinguish between more battery quantities in the future.

[timvolodine, 2014/09/23 19:04:39]

Done.

+</enum>
+
 <enum name="BlacklistSetup" type="int">
   <int value="0" label="Blacklist enabled"/>
   <int value="1" label="Blacklist ran successfully."/>