Fix AutoplayUmaHelper when autoplay is initiated from multiple sources

tools/metrics/rappor/rappor.xml

 <!--
 Copyright 2015 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome rappor metrics
 along with a detailed description for each histogram. See the design doc at
 http://www.chromium.org/developers/design-documents/rappor
@@ skipping 1344 matching lines @@
 <rappor-metric name="Media.Video.Autoplay.Muted.Attribute.Frame"
     type="ETLD_PLUS_ONE">
   <owner>avayvod@chromium.org</owner>
   <owner>mlamouri@chromium.org</owner>
   <owner>zqzhang@chromium.org</owner>
   <summary>
     The eTLD+1 of the frame URL that has an autoplay muted video by attribute.
   </summary>
 </rappor-metric>
 
+<rappor-metric name="Media.Video.Autoplay.Muted.DualSource.Frame"
+    type="ETLD_PLUS_ONE">
+  <owner>avayvod@chromium.org</owner>
+  <owner>mlamouri@chromium.org</owner>
+  <owner>zqzhang@chromium.org</owner>
+  <summary>
+    The eTLD+1 of the frame URL that has an autoplay muted video by both
+    attribute and play() method.
+  </summary>
+</rappor-metric>
+
 <rappor-metric name="Media.Video.Autoplay.Muted.PlayMethod.Frame"
     type="ETLD_PLUS_ONE">
   <owner>avayvod@chromium.org</owner>
   <owner>mlamouri@chromium.org</owner>
   <owner>zqzhang@chromium.org</owner>
   <summary>
     The eTLD+1 of the frame URL that has an autoplay muted video by play()
     method.
   </summary>
 </rappor-metric>
@@ skipping 1073 matching lines @@
     <flag bit="1" label="IS_REPEAT_VISIT"/>
     <summary>
       Bitfield of the state from an SSL warning interstitial.
     </summary>
   </flags-field>
 </rappor-metric>
 
 </rappor-metrics>
 
 </rappor-configuration>