Add the client for accessing Subresource Filter only list.

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 9658b2ee6db123ea65e1381698a0a5463d82d1bc..8d5a7a4fa9af5a1b85c61caeb5b6090ce53cedb8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -67709,12 +67709,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 
 <histogram name="SubresourceFilter.PageLoad.RedirectChainLength" units="urls">
   <owner>melandory@chromium.org</owner>
+  <suffix name="SubresourceFilterOnly"/>
   <summary>Total length of the server redirects during the navigation.</summary>
 </histogram>
 
 <histogram name="SubresourceFilter.PageLoad.RedirectChainMatchPattern"
     enum="SubresourceFilterMatchPattern">
   <owner>melandory@chromium.org</owner>
+  <suffix name="SubresourceFilterOnly"/>
   <summary>
     For each main frame navigation, records a pattern that indicates which URLs
     in the redirect chain matched Safe Browsing blacklists, and which did not.
@@ -120582,6 +120584,13 @@ value.
   <affected-histogram name="WebRTC.Stun.SuccessPercent.UnknownNAT"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="SubresourceFilterOnlyExperiment" separator=".">
+  <suffix name="SubresourceFilterOnly"/>
+  <affected-histogram name="SubresourceFilter.PageLoad.RedirectChainLength"/>
+  <affected-histogram
+      name="SubresourceFilter.PageLoad.RedirectChainMatchPattern"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="SyncModelType" separator=".">
   <suffix name="APP" label="APP"/>
   <suffix name="APP_LIST" label="APP_LIST"/>