Add high-precision timing histograms.

components/subresource_filter/content/renderer/subresource_filter_agent.cc

Index: components/subresource_filter/content/renderer/subresource_filter_agent.cc
diff --git a/components/subresource_filter/content/renderer/subresource_filter_agent.cc b/components/subresource_filter/content/renderer/subresource_filter_agent.cc
index 90c1230bd6ae917a715de1d708ee47e552083271..3ec326b5e0027bd0a4b50dfd93eb4a23b06c4944 100644
--- a/components/subresource_filter/content/renderer/subresource_filter_agent.cc
+++ b/components/subresource_filter/content/renderer/subresource_filter_agent.cc
@@ -11,6 +11,7 @@
 #include "components/subresource_filter/content/renderer/document_subresource_filter.h"
 #include "components/subresource_filter/content/renderer/ruleset_dealer.h"
 #include "components/subresource_filter/core/common/memory_mapped_ruleset.h"
+#include "components/subresource_filter/core/common/scoped_timers.h"
 #include "content/public/common/browser_side_navigation_policy.h"
 #include "content/public/renderer/render_frame.h"
 #include "ipc/ipc_message.h"
@@ -92,6 +93,17 @@ void SubresourceFilterAgent::RecordHistogramsOnLoadFinished() {
   UMA_HISTOGRAM_COUNTS_1000(
       "SubresourceFilter.DocumentLoad.NumSubresourceLoads.Disallowed",
       statistics.num_loads_disallowed);
+
+  UMA_HISTOGRAM_CUSTOM_MICRO_TIMES(

[engedy, 2016/11/30 12:42:28]

Please update unittests to verify that samples for these histograms are recorded
too.

[pkalinnikov, 2016/12/01 16:02:48]

Done.

+      "SubresourceFilter.DocumentLoad.SubresourceSums.Evaluation.WallDuration",

[engedy, 2016/11/30 12:42:28]

On second read, these histogram names sound a bit awkward, but I'm not sure.
What do you think about:

SubresourceFilter.DocumentLoad.SubresourceEvaluation.TotalWallDuration

Better, worse?

[Ilya Sherman, 2016/12/01 05:39:07]

+1

[pkalinnikov, 2016/12/01 16:02:48]

Done here and in histograms.xml.

+      statistics.evaluation_total_wall_duration,
+      base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(10),
+      50);
+  UMA_HISTOGRAM_CUSTOM_MICRO_TIMES(
+      "SubresourceFilter.DocumentLoad.SubresourceSums.Evaluation.CPUDuration",
+      statistics.evaluation_total_cpu_duration,
+      base::TimeDelta::FromMicroseconds(1), base::TimeDelta::FromSeconds(10),
+      50);
 }
 
 void SubresourceFilterAgent::OnDestruct() {