Implement the spring charger replacement UI.

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 fdfedefe751e97abf1dc02c787c2aa40074701a2..7111c4ed983bb705df05561479ffa120231e12af 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13765,6 +13765,13 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Power.ChargerType" enum="PowerChargerType">
+  <summary>
+    External power supply type such as MAINS_CHARGER, USB_CHARGER,
+    UNCONFIRMED_SPRING_CHARGER, SAFE_SPRING_CHARGER.

[Daniel Erat, 2013/12/10 21:30:36]

nit: document that a sample is reported every time a charger is connected to the
device

+  </summary>
+</histogram>
+
 <histogram name="Power.FirmwareResumeTimeOnAC" units="milliseconds">
   <summary>
     The time that the firmware took to resume the Chrome OS device from
@@ -27891,6 +27898,14 @@ other types of suffix sets.
   <int value="2" label="Brightness Absolute"/>
 </enum>
 
+<enum name="PowerChargerType" type="int">
+  <int value="0" label="Unknown charger"/>
+  <int value="1" label="MAINS charger"/>
+  <int value="2" label="USB Charger"/>
+  <int value="3" label="Unconfirmed Spring Charger"/>
+  <int value="4" label="Safe Spring Charger"/>
+</enum>
+
 <enum name="PreconnectedNavigation" type="int">
   <int value="0" label="No recent pre-connect to the page"/>
   <int value="1" label="Page nav. preceded by a pre-connect"/>