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 1dd9c545a78f4e7af695a67016fff27854fd05c0..7d485e7bfdfcc355097779c438b4c9a4e9519b4b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -33936,6 +33936,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="OfflinePages.ArchiveDirCreationTime" units="ms">
+  <owner>dewittj@chromium.org</owner>
+  <owner>jianli@chromium.org</owner>
+  <summary>
+    The amount of time to create the offline pages archive directory.
+  </summary>
+</histogram>
+
 <histogram name="OfflinePages.BatchDelete.Count">
   <owner>jianli@chromium.org</owner>
   <summary>Number of offline pages that are deleted in a batch.</summary>
@@ -34093,6 +34101,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="OfflinePages.ModelLoadTime" units="ms">
+  <owner>dewittj@chromium.org</owner>
+  <owner>jianli@chromium.org</owner>
+  <summary>
+    The amount of time to create the offline pages archive directory and load
+    the offline page model.

[Mark P, 2016/05/06 20:09:23]

nit: The histogram name implies this is merely model load time.  I think this is
a bit misleading.  If you think the time to create the archive directory is
small relative to the total load time then this misleading name is probably
okay.  If not, you should change the name.
Also, in general are you sure you want this histogram to include the earlier one
as opposed to two separate histograms, one for creation and one for loading?

[dewittj, 2016/05/06 20:13:15]

I do expect that directory creation will be negligible.  I'm not completely
sure, though, so I'm measuring it.
I'm most interested in the total time (dir + load), which is important for users
of the model.  I added the archive dir creation time as a way to see if that is
a significant part of the model load time.

Perhaps one way to make this a little more independent is to record the ratio of
archive directory creation time to total time.  Does that seem better to you?

[Mark P, 2016/05/06 20:18:39]

Can you spent a couple minutes thinking about a better histogram name that
reflects what it's actually measuring?
That seems worse because then you can't easily interpret a single number (say,
2.0) on its own.  How long is that?

+  </summary>
+</histogram>
+
 <histogram name="OfflinePages.OfflinePageCount">
   <owner>fgorski@chromium.org</owner>
   <owner>jianli@chromium.org</owner>