Remove PowerUsageMonitor.

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 359d0e781a986b77fad25f189dd8cd57338dd44f..79ebb09994cabd16981a76b0704df2ea250a0e0f 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -50241,6 +50241,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Power.BatteryDischargePercentPerHour" units="%">
+  <obsolete>
+    Deprecated 02/2017 in favor of power benchmarks that have less variability
+    than data from users' machines.
+  </obsolete>
   <owner>jeremy@chromium.org</owner>
   <summary>
         The percentage of battery capacity used per hour relative to a full
@@ -50267,6 +50271,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Power.BatteryDischargeRate_15" units="%">
+  <obsolete>
+    Deprecated 02/2017 in favor of power benchmarks that have less variability
+    than data from users' machines.
+  </obsolete>
   <owner>jeremy@chromium.org</owner>
   <summary>
         The percent of depleted battery capacity relative to a full battery over
@@ -50281,6 +50289,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Power.BatteryDischargeRate_30" units="%">
+  <obsolete>
+    Deprecated 02/2017 in favor of power benchmarks that have less variability
+    than data from users' machines.
+  </obsolete>
   <owner>jeremy@chromium.org</owner>
   <summary>
         The percent of depleted battery capacity relative to a full battery over
@@ -50295,6 +50307,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="Power.BatteryDischargeRate_5" units="%">
+  <obsolete>
+    Deprecated 02/2017 in favor of power benchmarks that have less variability
+    than data from users' machines.
+  </obsolete>
   <owner>jeremy@chromium.org</owner>
   <summary>
         The percent of depleted battery capacity relative to a full battery over