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 0e344eb8b5f4cb5a41835ed181b3841e832e788c..328a154593586f5ac5c131a578b718e90e9d155c 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -67152,12 +67152,14 @@ 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="SubresourceFilter"/>

[jwd, 2017/02/17 22:40:32]

I don't think this does anything. You need to have a <histogram_suffixes> tag in
the histogram_suffixes_list. Documentation for this is at the top of the file.

[melandory, 2017/02/28 12:16:05]

Done.

   <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.