Add high-precision timing histograms.

components/subresource_filter/core/browser/ruleset_service.cc

Index: components/subresource_filter/core/browser/ruleset_service.cc
diff --git a/components/subresource_filter/core/browser/ruleset_service.cc b/components/subresource_filter/core/browser/ruleset_service.cc
index 3a0c5fcb3a4b2992e3bf3e8efc2b06a4231e9f00..031a1f08dc57113965f325c2f19dc3e631583062 100644
--- a/components/subresource_filter/core/browser/ruleset_service.cc
+++ b/components/subresource_filter/core/browser/ruleset_service.cc
@@ -28,6 +28,7 @@
 #include "components/subresource_filter/core/common/copying_file_stream.h"
 #include "components/subresource_filter/core/common/indexed_ruleset.h"
 #include "components/subresource_filter/core/common/proto/rules.pb.h"
+#include "components/subresource_filter/core/common/scoped_timers.h"
 #include "components/subresource_filter/core/common/unindexed_ruleset.h"
 #include "third_party/protobuf/src/google/protobuf/io/zero_copy_stream_impl_lite.h"
 
@@ -344,6 +345,8 @@ IndexedRulesetVersion RulesetService::IndexAndWriteRuleset(
 bool RulesetService::IndexRuleset(base::File unindexed_ruleset_file,
                                   RulesetIndexer* indexer) {
   SCOPED_UMA_HISTOGRAM_TIMER("SubresourceFilter.IndexRuleset.WallDuration");
+  SCOPED_UMA_HISTOGRAM_THREAD_TIMER(
+      "SubresourceFilter.IndexRuleset.CPUDuration");
 
   int64_t unindexed_ruleset_size = unindexed_ruleset_file.GetLength();
   CopyingFileInputStream copying_stream(std::move(unindexed_ruleset_file));