Log to UMA when x-origin frames (1) are created and (2) become visible

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 e7e8a1865bd2f6510381b07820480d05b93165f5..c610f5b96acd270dd36c7fbfe0a46421e3f0a1ac 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -17043,6 +17043,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="FrameLoading.Deferred.StateCountsV1"
+    enum="FrameStateForDeferredLoading">
+  <owner>dgrogan@chromium.org</owner>
+  <summary>
+    Why and if subframes would be loaded in a world where we defer loading until
+    they are visible or are important for cross-origin communication.
+  </summary>
+</histogram>
+
 <histogram name="GCM.AndroidGcmReceiverError" enum="GcmReceiverStatus">
   <owner>khushalsagar@chromium.org</owner>
   <obsolete>
@@ -80007,6 +80016,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="3" label="Allowed navigation, user gesture"/>
 </enum>
 
+<enum name="FrameStateForDeferredLoading" type="int">
+  <int value="0" label="Created"/>
+  <int value="1" label="WouldLoadBecauseVisible"/>
+</enum>
+
 <enum name="FtpDataConnectionError" type="int">
   <int value="0">Data connection successful</int>
   <int value="1">Local firewall blocked the connection</int>