UMA metrics for LogDnsClient

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 dc2c0963d45428a648904c68fa96c009dc55ce8d..a03177fdb7207220772131d559f159d465a8a4d4 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -28969,10 +28969,29 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
     24 hours after the timestamp in the SCT (24 hours being the typical Maximum
     Merge Delay).
   </summary>
 </histogram>
 
+<histogram name="Net.CertificateTransparency.DnsQueryDuration" units="ms">
+  <owner>robpercival@chromium.org</owner>
+  <summary>
+    The time taken to obtain an inclusion proof from a Certificate Transparency
+    log over DNS. This includes the time taken to obtain the leaf index first.
+    Emitted at the end of an attempt.
+  </summary>
+</histogram>
+
+<histogram name="Net.CertificateTransparency.DnsQueryStatus"
+    enum="CertificateTransparencyDnsQueryStatus">
+  <owner>robpercival@chromium.org</owner>
+  <summary>
+    The status of each attempt to obtain an inclusion proof from a Certificate
+    Transparency log over DNS. This can consist of more than one DNS request.
+    Emitted at the end of an attempt.
+  </summary>
+</histogram>
+
 <histogram name="Net.CertificateTransparency.MainFrameValidSCTCount">
   <owner>eranm@chromium.org</owner>
   <summary>
     Number of valid Signed Certificate Timestamps (SCTs) present for the
     main-frame resource. Emitted every time a main-frame resource is fetched.
@@ -76121,10 +76140,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
     https://crbug.com/522312
   </obsolete>
   <int value="0" label="Root Certificate"/>
 </enum>
 
+<enum name="CertificateTransparencyDnsQueryStatus" type="int">
+  <int value="0" label="SUCCESS"/>
+  <int value="1" label="FAIL_MISC"/>
+  <int value="2" label="FAIL_NAME_RESOLUTION"/>
+  <int value="3" label="FAIL_LEAF_INDEX_MALFORMED"/>
+  <int value="4" label="FAIL_INCLUSION_PROOF_MALFORMED"/>
+</enum>
+
 <enum name="ChannelLayout" type="int">
   <int value="0" label="CHANNEL_LAYOUT_NONE"/>
   <int value="1" label="CHANNEL_LAYOUT_UNSUPPORTED"/>
   <int value="2" label="CHANNEL_LAYOUT_MONO"/>
   <int value="3" label="CHANNEL_LAYOUT_STEREO"/>