Add histograms to record the severity scores for certain SSL errors.

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 5f6cffbc3a81186f5c6da1a79d3230a4b40e6fcb..d5d8c48ec639394298b7d1e11047a755f33e9393 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -10509,6 +10509,24 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="interstitial.ssl.severity_score.common_name_invalid" units="%">
+  <owner>felt@chromium.org</owner>
+  <summary>
+    The likelihood of an error being an attack for the
+    |CERT_COMMON_NAME_INVALID| error. Higher the percentage, higher the

[Mark P, 2014/09/10 20:41:36]

For the first sentence, do you mean:
The likelihood of an CERT_COMMON_NAME_INVALID error being an attack.
?

[Mark P, 2014/09/10 20:41:36]

nit: higher -> the higher
(two places)

Or omit the last sentence entirely.  Personally, I don't think it adds anything.

[palmer, 2014/09/11 18:03:48]

Done.

[palmer, 2014/09/11 18:03:48]

Done.

+    probability of an error being an attack.
+  </summary>
+</histogram>
+
+<histogram name="interstitial.ssl.severity_score.date_invalid" units="%">
+  <owner>felt@chromium.org</owner>
+  <summary>
+    The likelihood of an error being an attack for the |CERT_DATE_INVALID|
+    error. Higher the percentage, higher the probability of an error being an
+    attack.
+  </summary>
+</histogram>
+
 <histogram name="interstitial.ssl_accept_time" units="milliseconds">
   <obsolete>
     Removed on 8/1/13.