Add Mist.SwitchResult histogram.

Related CL: https://chromium-review.googlesource.com/#/c/169440/

BUG=290248

Review URL: https://chromiumcodereview.appspot.com/24187003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223572 0039d316-1c4b-4281-b951-d872f2087c98

tools/metrics/histograms/histograms.xml

@@ -6224,6 +6224,13 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Mist.SwitchResult" enum="MistSwitchResult">
+  <summary>
+    The result (e.g. success or the type of failure) of a modem interface switch
+    operation performed by mist on Chrome OS.
+  </summary>
+</histogram>
+
 <histogram name="Mouse.PointerSensitivity.Changed" enum="PointerSensitivity">
   <summary>
     Tracks mouse sensitivity setting changes by the user. This replaces the old
@@ -22863,6 +22870,11 @@ other types of suffix sets.
   <int value="3" label="kInvalidPlayerState"/>
 </enum>
 
+<enum name="MistSwitchResult" type="int">
+  <int value="0" label="Success"/>
+  <int value="1" label="Failure"/>
+</enum>
+
 <enum name="MobileSessionCallerApp" type="int">
   <int value="0" label="Google Search"/>
   <int value="1" label="GMail"/>