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 0b8814dcb5fa9038c933c872745555b49bd0dd77..ef67daad51fbaa7f6f297fa2d6bf7d1ab7bb60a6 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -62279,6 +62279,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Microseconds spent in Document::updateStyle.</summary>
 </histogram>
 
+<histogram name="SubresourceFilter.DocumentLoad.Activation.CPUDuration"
+    units="us">

[Ilya Sherman, 2016/11/18 22:26:05]

nit: s/us/microseconds (and if you wouldn't mind, it would be great to update
tools/metrics/histograms/pretty_print.py with that preference -- possibly in a
separate CL if there are existing violations)

[pkalinnikov, 2016/11/21 14:51:00]

Done. I didn't find any histogram in "histograms.xml" that would measure in
microseconds, but wouldn't have "microseconds" as its unit. Since I use
"microseconds" too, does it make sense to update the pretty_print.py script?

[Ilya Sherman, 2016/11/22 00:02:47]

Yes, please go ahead and update
https://cs.chromium.org/chromium/src/tools/metrics/histograms/pretty_print.py...
in that case.

[pkalinnikov, 2016/11/24 13:40:09]

Updated the script. Please take a look.

+  <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="ms">

[Ilya Sherman, 2016/11/18 22:26:05]

Why are the two types of histograms using different units?  I'd expect the times
to be pretty similar, no?

[pkalinnikov, 2016/11/21 14:51:00]

My bad. Fixed.

+  <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>
@@ -62342,6 +62360,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SubresourceFilter.IndexRuleset.CPUDuration" units="us">
+  <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>
@@ -62378,6 +62406,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SubresourceFilter.SubresourceLoad.Evaluation.CPUDuration"
+    units="us">
+  <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.
+  </summary>
+</histogram>
+
+<histogram name="SubresourceFilter.SubresourceLoad.Evaluation.WallDuration"
+    units="ms">
+  <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.
+  </summary>
+</histogram>
+
 <histogram name="SubresourceFilter.WriteRuleset.ReplaceFileError"
     enum="PlatformFileError">
   <owner>engedy@chromium.org</owner>