Added UMA statistics for changing the active window via click or touch events.

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 0990180eeba760cd72bda8669dec39d28f30bdaf..87bcdd418b135df7dc40c1535c8ff98738ffbc6f 100644
--- a/tools/metrics/actions/actions.xml
+++ b/tools/metrics/actions/actions.xml
@@ -2501,6 +2501,15 @@ 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="Desktop_SwitchTask">
+  <owner>bruthig@google.com</owner>
+  <owner>tdanderson@google.com</owner>
+  <description>
+    Recorded when the user activates an existing task by clicking or tapping on
+    it in the 2-dimensional screen space.
+  </description>
+</action>
+
 <action name="Destination_Application_Edit">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <description>Please enter the description of this user action.</description>