Add TimeToScrollUpdateSwapBegin2 in RAPPOR

tools/metrics/rappor/rappor.xml

Index: tools/metrics/rappor/rappor.xml
diff --git a/tools/metrics/rappor/rappor.xml b/tools/metrics/rappor/rappor.xml
index f8a23ed82c173273afc1d6f11801a835b471e513..d3d934bb32804347e681089cd991f430c3935032 100644
--- a/tools/metrics/rappor/rappor.xml
+++ b/tools/metrics/rappor/rappor.xml
@@ -909,6 +909,30 @@ components/rappor/rappor_parameters.h.
   </summary>
 </rappor-metric>
 
+<rappor-metric
+    name="Event.Latency.ScrollUpdate.Touch.TimeToScrollUpdateSwapBegin2"
+    type="UMA_RAPPOR_TYPE">
+  <owner>nzolghadr@chromium.org</owner>
+  <owner>tdresser@chromium.org</owner>
+  <summary>
+    The eTLD+1 of the website visited, along with a the time between the initial
+    creation of a touch event and the start of the frame swap on the GPU service
+    caused by the generated ScrollUpdate gesture event if that ScrollUpdate is
+    the first such event in a given scroll gesture event sequence. If no swap
+    was induced by the event, no recording is made.
+  </summary>
+  <string-field name="Domain">
+    <summary>
+      The domain+registry of the URL.
+    </summary>
+  </string-field>
+  <uint64-field name="Latency">
+    <summary>
+      Latency in microseconds representing Touch.TimeToScrollUpdateSwapBegin.
+    </summary>
+  </uint64-field>
+</rappor-metric>
+
 <rappor-metric name="Extensions.AffectedByIsolateExtensions"
     type="UMA_RAPPOR_TYPE">
   <owner>nick@chromium.org</owner>