Add UMA metric for tracking listeners for blocking touch before page finished loading

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 e0b750e8533e5e435c0f956b7fd3b1204f2ccb8c..f965cd76d802049bbc498f8e4132a77405cc903b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -12001,6 +12001,26 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Event.Touch.TouchDispositionsAfterPageLoad"
+    enum="TouchEventDispatchResultType">
+  <owner>tdresser@chromium.org</owner>
+  <summary>
+    Records the disposition (handled or not handled) of touch start events and
+    the first touchmove events per scroll. Only recorded after the page is fully
+    loaded.
+  </summary>
+</histogram>
+
+<histogram name="Event.Touch.TouchDispositionsBeforePageLoad"
+    enum="TouchEventDispatchResultType">
+  <owner>tdresser@chromium.org</owner>
+  <summary>
+    Records the disposition (handled or not handled) of touch start events and
+    the first touchmove events per scroll. Only recorded before the page is
+    fully loaded.
+  </summary>
+</histogram>
+
 <histogram name="Event.TouchDuration" units="ms">
   <owner>kuscher@google.com</owner>
   <owner>rbyers@chromium.org</owner>
@@ -85255,6 +85275,11 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="3" label="CLIENT_NO_CHANNEL_ID_SERVICE"/>
 </enum>
 
+<enum name="TouchEventDispatchResultType" type="int">
+  <int value="0" label="Unhandled touch events"/>
+  <int value="1" label="Handled touch events"/>
+</enum>
+
 <enum name="TouchEventsState" type="int">
   <int value="0" label="Enabled"/>
   <int value="1" label="Automatic - enabled"/>