Add high-precision timing histograms.

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 856d9955fc5ad0ec94a1d83b1dabbf178804f6c9..c2f6568aeadd199b858958f7b243e7d5ccd48390 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4148,7 +4148,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Image codec inferred during decode.</summary>
 </histogram>
 
-<histogram name="Blink.Fetch.RequestResourceTime" units="us">
+<histogram name="Blink.Fetch.RequestResourceTime" units="microseconds">
   <owner>csharrison@chromium.org</owner>
   <summary>
     The total microseconds spent in ResourceFetcher::requestResource.
@@ -48261,7 +48261,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="PreloadScanner.ExternalCSS.ScanTime" units="us">
+<histogram name="PreloadScanner.ExternalCSS.ScanTime" units="microseconds">
   <owner>csharrison@chromium.org</owner>
   <summary>
     Microseconds it took to scan the first chunk of external CSS for preloads.
@@ -63514,18 +63514,36 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="Style.AuthorStyleSheet.ParseTime" units="us">
+<histogram name="Style.AuthorStyleSheet.ParseTime" units="microseconds">
   <owner>csharrison@chromium.org</owner>
   <summary>
     Microseconds spent in StyleSheetContents::parseAuthorStyleSheet.
   </summary>
 </histogram>
 
-<histogram name="Style.UpdateTime" units="us">
+<histogram name="Style.UpdateTime" units="microseconds">
   <owner>csharrison@chromium.org</owner>
   <summary>Microseconds spent in Document::updateStyle.</summary>
 </histogram>
 
+<histogram name="SubresourceFilter.DocumentLoad.Activation.CPUDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Records how much thread CPU time it takes to decide whether subresource
+    filtering should be activated for a main frame or subframe.
+  </summary>
+</histogram>
+
+<histogram name="SubresourceFilter.DocumentLoad.Activation.WallDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Records how long it takes to decide whether subresource filtering should be
+    activated for a main frame or subframe.
+  </summary>
+</histogram>
+
 <histogram name="SubresourceFilter.DocumentLoad.ActivationState"
     enum="SubresourceFilterActivationState">
   <owner>engedy@chromium.org</owner>
@@ -63589,6 +63607,39 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram
+    name="SubresourceFilter.DocumentLoad.SubresourceEvaluation.TotalCPUDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Whenever a document load is finished in a main frame or subframe with
+    subresource filtering activated, records the total thread CPU time spent on
+    processing subresource requests in allowLoad.
+  </summary>
+</histogram>
+
+<histogram
+    name="SubresourceFilter.DocumentLoad.SubresourceEvaluation.TotalWallDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Whenever a document load is finished in a main frame or subframe with
+    subresource filtering activated, records the total real time spent on
+    processing subresource requests in allowLoad, including the time spent on
+    waiting or being descheduled.
+  </summary>
+</histogram>
+
+<histogram name="SubresourceFilter.IndexRuleset.CPUDuration" units="ms">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    The total CPU time it took to parse and index all rules. Does not include
+    time when the indexing thread was not doing actual work, e.g. waiting for
+    I/O or being descheduled. Recorded every time the RulesetService kicks off a
+    ruleset indexing process.
+  </summary>
+</histogram>
+
 <histogram name="SubresourceFilter.IndexRuleset.NumUnsupportedRules"
     units="rules">
   <owner>engedy@chromium.org</owner>
@@ -63643,6 +63694,26 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SubresourceFilter.SubresourceLoad.Evaluation.CPUDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Whenever a subresource of a document is evaluated against the ruleset,
+    records the thread CPU time spent on calculating whether it should be
+    allowed to load.
+  </summary>
+</histogram>
+
+<histogram name="SubresourceFilter.SubresourceLoad.Evaluation.WallDuration"
+    units="microseconds">
+  <owner>pkalinnikov@chromium.org</owner>
+  <summary>
+    Whenever a subresource of a document is evaluated against the ruleset,
+    records how much time was spent on calculating whether it should be allowed
+    to load.
+  </summary>
+</histogram>
+
 <histogram name="SubresourceFilter.WriteRuleset.ReplaceFileError"
     enum="PlatformFileError">
   <owner>engedy@chromium.org</owner>