Add UMA to hotword trigger extension.

tools/metrics/actions/actions.xml

Index: tools/metrics/actions/actions.xml
diff --git a/tools/metrics/actions/actions.xml b/tools/metrics/actions/actions.xml
index b0f8f6f93d8edf2b9aaff09c9be8118d619fa18d..e67d0c09020906bf80fe6352afe702000cf88b95 100644
--- a/tools/metrics/actions/actions.xml
+++ b/tools/metrics/actions/actions.xml
@@ -3130,6 +3130,16 @@ should be able to be added at any place in this file.
   <description>Please enter the description of this user action.</description>
 </action>
 
+<action name="Hotword.HotwordTrigger">
+  <owner>amistry@chromium.org</owner>
+  <owner>rlp@chromium.org</owner>
+  <owner>somast@chromium.org</owner>
+  <description>
+    Counts the number of times the hotword was triggered by the user saying 'Ok

[Mark P, 2014/10/21 17:33:05]

Actions are not count.  Actions are events with timestamps.  If you only want a
count, use a histogram instead.  If you want an action, try a description like:
User triggered the hotword by saying 'Ok Google'.

[Anand Mistry (off Chromium), 2014/10/21 23:19:26]

Done.

+    Google'.
+  </description>
+</action>
+
 <action name="ImportLockDialogCocoa_Shown">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>