[Autoplay] Add histogram metrics for cross-origin autoplay muted experiment

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 ccde36a65a7663ea7e90dda0f672231c2cc3d8f2..f3346395631f74e754994e8bbf76e166a0ad34dc 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -24258,6 +24258,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Media.Autoplay.CrossOrigin.Result"
+    enum="CrossOriginAutoplayResult">
+  <owner>avayvod@chromium.org</owner>
+  <owner>mlamouri@chromium.org</owner>
+  <owner>zqzhang@chromium.org</owner>
+  <summary>
+    The result of autoplaying video elements in cross-origin iframes.
+  </summary>
+</histogram>
+
 <histogram name="Media.AVDA.FrameSentAsOverlay" enum="BooleanFrameAsOverlay">
   <owner>liberato@chromium.org</owner>
   <summary>
@@ -80427,6 +80437,13 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="8" label="PlayMusic"/>
 </enum>
 
+<enum name="CrossOriginAutoplayResult" type="int">
+  <int value="0" label="Allowed"/>
+  <int value="1" label="Blocked"/>
+  <int value="2" label="PlayedWithGesture"/>
+  <int value="3" label="UserPaused"/>
+</enum>
+
 <enum name="CrosTPMDictionaryAttackResetStatusEnum" type="int">
   <int value="0" label="Reset not necessary"/>
   <int value="1" label="Reset attempt succeeded"/>