chromeos: Add descriptions for power manager metrics.

tools/metrics/histograms/histograms.xml

 <!--
 Copyright 2013 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
@@ skipping 6295 matching lines @@
 <histogram name="Plugin.PpapiBrokerLoadResult" enum="PluginLoadResult">
   <summary>The result from an attempt to load a PPAPI broker.</summary>
 </histogram>
 
 <histogram name="Plugin.PpapiPluginLoadResult" enum="PluginLoadResult">
   <summary>The result from an attempt to load a PPAPI plugin.</summary>
 </histogram>
 
 <histogram name="Power.BacklightLevelOnAC" units="%">
   <summary>
-    The level of the backlight as a percentage when the user is on AC.
+    The level of the backlight as a percentage when the user is on AC. Sampled
+    every 30 seconds.
   </summary>
 </histogram>
 
 <histogram name="Power.BacklightLevelOnBattery" units="%">
   <summary>
     The level of the backlight as a percentage when the user is on battery.
+    Sampled every 30 seconds.
   </summary>
 </histogram>
 
 <histogram name="Power.BatteryChargeHealth" units="%">
   <summary>
     Chrome OS battery charge health percentage.  Sampled once when device starts
     charging.
   </summary>
 </histogram>
 
-<histogram name="Power.BatteryDischargeRate">
+<histogram name="Power.BatteryDischargeRate" units="mW">
   <summary>
-    Chrome OS battery discharge rate in mW sampled when the device runs on
-    battery.
+    Chrome OS battery discharge rate in mW sampled every 30 seconds while the
+    device runs on battery.
   </summary>
 </histogram>
 
+<histogram name="Power.BatteryDischargeRateWhileSuspended" units="mW">
+  <summary>
+    Chrome OS battery discharge rate in mW while the system was suspended,
+    sampled at resume. Only reported if the system was on battery power both
+    before suspending and after resuming, if the energy level didn't increase
+    while suspended (which would indicate that an AC adapter was connected), and
+    if the system was suspended for at least a minute.
+  </summary>
+</histogram>
+
 <histogram name="Power.BatteryInfoSample" enum="BatteryInfoSampleResult">
   <summary>
     Counts the number of times we have read the battery status from sysfs and if
     it gave us sensible values.
   </summary>
 </histogram>
 
 <histogram name="Power.BatteryRemainingAtEndOfSessionOnAC" units="%">
   <summary>
     Chrome OS remaining battery charge as percent of the maximum battery charge,
@@ skipping 158 matching lines @@
   </summary>
 </histogram>
 
 <histogram name="Power.KernelSuspendTimeOnBattery" units="milliseconds">
   <summary>
     The time that the kernel took to suspend-to-RAM the Chrome OS device when
     running on battery.
   </summary>
 </histogram>
 
+<histogram name="Power.KeyboardBacklightLevel" units="%">
+  <summary>
+    The level of the keyboard backlight as a percentage. Sampled every 30
+    seconds.
+  </summary>
+</histogram>
+
+<histogram name="Power.KeyboardBrightnessAdjust" enum="PowerBrightnessAdjust">
+  <summary>
+    Number of times the user has adjusted keyboard backlight brightness up and

[jar (doing other things), 2013/05/24 17:09:03]

When is this sampled?  At shutdown???  Each time the the system sleeps?

[Daniel Erat, 2013/05/24 22:02:29]

As discussed over IM, I've removed this histogram -- Chrome already reports
these adjustments as user actions.

I'm also removing the Power.BacklightLevel* histograms in conjunction with a
power manager change to stop reporting them. Is it acceptable to remove the
descriptions for them in this change, or should the descriptions be retained
indefinitely (since they have previously been reported)?

+    down.
+  </summary>
+</histogram>
+
 <histogram name="Power.LengthOfSession" units="seconds">
   <summary>
     The length of time, in seconds, that a user spent in a single session.
     Values for this metric are clamped to 12 hours, so the last bucket should be
     considered to be including all metrics above 12 hours.
   </summary>
 </histogram>
 
 <histogram name="Power.MilliConsumptionPerHourIosOnActive">
   <summary>
@@ skipping 8849 matching lines @@
 <fieldtrial name="SSLResumption">
   <group name="Resume_Handshake" label="Session Resumption"/>
   <group name="Full_Handshake" label="Full"/>
   <affected-histogram name="Net.SSL_Connection_Latency"/>
   <affected-histogram name="Net.SSL_Connection_Latency_Google"/>
 </fieldtrial>
 
 </fieldtrials>
 
 </histogram-configuration>