Adding DiskBasedCertCache to HttpCache (+UMA).

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 e35ae92e0c9f08a2a52273a11e3c56362403f57b..44b832514b25ef39b2ab241804279e473ef29c24 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3499,6 +3499,118 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="DiskBasedCertCache.ChainReadTime" units="milliseconds">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Measures the wall clock time from when the reading of a certificate chain to

[wtc, 2014/07/09 21:11:51]

Nit: to disk cache => from disk cache

+    disk cache is issued until the last certificate is retrieved.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.ChainWriteTime" units="milliseconds">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Measures the wall clock time from when the writing of a certificate chain to
+    disk cache is issued until the last certificate is written.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.ReadSuccessInt1" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the first intermediate certificate in a certificate chain was
+    successfully read from the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.ReadSuccessInt2" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the second intermediate certificate in a certificate chain
+    was successfully read from the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.ReadSuccessIntN" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the Nth (not including the first or second) intermediate
+    certificate in a certificate chain was successfully read from the disk
+    cache.
+  </summary>
+</histogram>

[jar (doing other things), 2014/07/09 22:12:01]

nit: You may find it nicer to have two histograms, on for "successfully reading"
and one for "failed reading".  

Probably use a UMA_CUSTOM_HISTOGRAM("names...", sample, 1, 10, 7);



Also (perhaps), the clever way to naim these is to have *only* the final postfix
vary, and then use the <field_trial> construct so that you don't have to repeat
the prose.

DiskBasedCertCache.ReadNthCertificateFailure
DiskBasedCertCache.ReadNthCertificateSuccess

You'd write the bulk of the prose for:
DiskBasedCertCache.ReadNthCertificate

end then have a <field_trial> that lists two alternative extensions (use the
separator="" form).

+
+<histogram name="DiskBasedCertCache.ReadSuccessLeaf" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the leaf certificate of a certificate chain was successfuly
+    read from the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.ReadSuccessRoot" enum="BooleanSuccess">

[jar (doing other things), 2014/07/09 22:12:01]

This may nicely fall into the above histogram, using root==0 (as you suggested
offline).

+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the root certificate of a certificate chain was successfuly
+    read from the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.ReadSuccessTotal" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not a certificate was successfuly read from the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.WriteSuccessInt1" enum="BooleanSuccess">

[jar (doing other things), 2014/07/09 22:12:01]

This will be a lot like the read histograms... sooooo... perhaps you could have
a common prefix like:


DiskBasedCertCache.ValidIoWriteSuccess
DiskBasedCertCache.ValidIoWriteFailure
DiskBasedCertCache.ValidIoReadSuccess
DiskBasedCertCache.ValidIoReadFailure

So have a nice bit of prose for:

DiskBasedCertCache.ValidIo

Then have a field trial to extend that for the four cases.

+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the first intermediate certificate in a certificate chain was
+    successfully written to the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.WriteSuccessInt2" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the second intermediate certificate in a certificate chain
+    was successfully written to the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.WriteSuccessIntN" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the Nth (not including the first or second) intermediate
+    certificate in a certificate chain was successfully written to the disk
+    cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.WriteSuccessLeaf" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the leaf certificate of a certificate chain was successfully
+    written to the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.WriteSuccessRoot" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not the root certificate of a certificate chain was successfully
+    written to the disk cache.
+  </summary>
+</histogram>
+
+<histogram name="DiskBasedCertCache.WriteSuccessTotal" enum="BooleanSuccess">
+  <owner>brandonsalmon@chromium.org</owner>
+  <summary>
+    Whether or not a certificate was successfully written to the disk cache.
+  </summary>
+</histogram>
+
 <histogram name="DiskCache.0.FilesAge" units="hours">
   <owner>rvargas@chromium.org</owner>
   <summary>The age of the cache's files (wall time).</summary>