UMA stats for stylus usage

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 e4e29aeeb7dda960671391a639ab42e29e5de9e1..69d5034b79cd6f06d7739b6d944464dc2d292dc4 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -13040,8 +13040,21 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.DownEventCount.PerDestination"
+    enum="DownEventDestination">
+  <owner>xiaoyinh@chromium.org</owner>
+  <owner>tbuckley@chromium.org</owner>
+  <summary>
+    The number of down events received per destination. Every down event that is
+    targeted to each destination will be counted, including those that don't
+    have an effect. For example: Tapping on a disabled button inside the browser
+    frame will be treated as down events on browser window.
+  </summary>
+</histogram>
+
 <histogram name="Event.DownEventCount.PerFormFactor" enum="DownEventFormFactor">
   <owner>xiaoyinh@chromium.org</owner>
+  <owner>tbuckley@chromium.org</owner>
   <summary>
     Counts the number of down events generated by clamshell/touchview.
   </summary>
@@ -13049,6 +13062,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="Event.DownEventCount.PerInput" enum="DownEventSource">
   <owner>xiaoyinh@chromium.org</owner>
+  <owner>tbuckley@chromium.org</owner>
   <summary>
     Counts the number of down events generated by Mouse/Touch/Stylus.
   </summary>
@@ -76828,6 +76842,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="GET_NON_CACHABLE"/>
 </enum>
 
+<enum name="DownEventDestination" type="int">
+  <int value="0" label="Others, everything except browser and apps"/>
+  <int value="1" label="Inside the browser frame"/>
+  <int value="2" label="Regular chrome app, except default note-taking app"/>
+  <int value="3" label="ARC app (android app on Chrome)"/>
+  <int value="4" label="Default note-taking app"/>
+</enum>
+
 <enum name="DownEventFormFactor" type="int">
   <int value="0" label="Clamshell"/>
   <int value="1" label="Touchview"/>