Add page-level aggregation of SubresourceFilter time metrics.

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 456e5f4a83e30f559265773946e25da076915bbf..56a2c095ca089f23d7043c79d92f9549ee76a537 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -64543,6 +64543,29 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="SubresourceFilter.PageLoad.SubresourceEvaluation.TotalCPUDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Whenever a page load is finished with subresource filtering activated,
+    records the total thread CPU time spent on evaluating subresource requests,
+    aggregated across all frames.
+  </summary>
+</histogram>
+
+<histogram
+    name="SubresourceFilter.PageLoad.SubresourceEvaluation.TotalWallDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Whenever a page load is finished with subresource filtering activated,
+    records the total real time spent on evaluating subresource requests,
+    aggregated across all frames. This includes the time spent on waiting or
+    being descheduled.
+  </summary>
+</histogram>
+
 <histogram name="SubresourceFilter.Prompt.NumReloads" enum="BooleanRequested">
   <owner>melandory@chromium.org</owner>
   <summary>