[subresource_filter] SB throttle can send multiple speculative requests.

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 c5a6a1051d3ab145f47801f6850103b3fd4ca7ec..c3bcace85cb1317295bd1b75dff533b110037f6b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -71150,6 +71150,26 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SubresourceFilter.PageLoad.SafeBrowsingDelay" units="ms">
+  <owner>csharrison@chromium.org</owner>
+  <summary>
+    The navigation delay imposed by the subresource filter on a given navigation
+    due to Safe Browsing checks.
+  </summary>
+</histogram>
+
+<histogram
+    name="SubresourceFilter.PageLoad.SafeBrowsingDelay.NoRedirectSpeculation"
+    units="ms">
+  <owner>csharrison@chromium.org</owner>
+  <summary>
+    The navigation delay that would have been imposed by the subresource filter
+    on a given navigation due to Safe Browsing checks if redirect speculation
+    was removed. Removing this feature would cause more delay if a navigation
+    has redirects.
+  </summary>
+</histogram>
+
 <histogram
     name="SubresourceFilter.PageLoad.SubresourceEvaluation.TotalCPUDuration"
     units="microseconds">
@@ -71192,6 +71212,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SubresourceFilter.SafeBrowsing.CheckTime" units="ms">
+  <owner>csharrison@chromium.org</owner>
+  <summary>
+    The time an individual Safe Browsing URL check took before finishing. Logged
+    when a check is complete or cancelled due to a timeout.
+  </summary>
+</histogram>
+
 <histogram name="SubresourceFilter.SubresourceLoad.Evaluation.CPUDuration"
     units="microseconds">
   <owner>pkalinnikov@chromium.org</owner>