Add Certificate Transparency logs auditing

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 11f243c887a498ed580e0ea96e788ccf7158ebe2..8175c1c3bbf5814dd4457884aec73dc270336679 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -30271,6 +30271,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Net.CertificateTransparency.InclusionCheckResult"
+    enum="CTLogEntryInclusionCheckResult">
+  <owner>eranm@chromium.org</owner>
+  <summary>
+    The result of an inclusion check for a Certificate Transparency log entry
+    (composed of a TLS certificate observed together with Signed Certificate
+    Timestamps). Emitted once per (TLS certificate, Signed Certificate
+    Timestamp) pair observed and checked for inclusion (check results are
+    cached).
+  </summary>
+</histogram>
+
 <histogram name="Net.CertificateTransparency.MainFrameValidSCTCount">
   <owner>eranm@chromium.org</owner>
   <summary>
@@ -82075,6 +82087,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="194" label="TSS Error Unknown Error"/>
 </enum>
 
+<enum name="CTLogEntryInclusionCheckResult" type="int">
+  <int value="0" label="Obtained valid inclusion proof"/>
+  <int value="1" label="Failed getting inclusion proof"/>
+  <int value="2" label="Obtained inclusion proof is invalid"/>
+</enum>
+
 <enum name="CTRequirementCompliance" type="int">
   <obsolete>
     Deprecated 1/2016.