Forget SSL error exceptions when good certs seen for regular requests.

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 b6b847c1221ef15f3a1d08a00eea01802688a550..69a77f3015d6655eec76f731135597044bd24018 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -12740,6 +12740,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="interstitial.ssl.good_cert_seen" enum="SSLGoodCertSeenEvent">
+  <owner>jww@chromium.org</owner>
+  <summary>
+    Tracks how often a good certificate is seen when a user has already given an
+    exception for a bad certificate. Recorded any time a new connection is made

[Mark P, 2015/04/17 16:20:36]

This first sentence is a bit wrong (it doesn't track how often anything happens)
and slightly backwards.  Perhaps something like this:
Records whether the user has already given an exception for a bad certificate on
this site.

[jww, 2015/04/17 18:14:33]

Hm, that's not entirely accurate either because it's only recorded when a good
certificate is seen (not when the cert has an error). I've updated it to:

"Records when a good certificate is seen after a user already gave an exception
for a bad certificate for the same host."

+    with a good certificate.
+  </summary>
+</histogram>
+
 <histogram name="interstitial.ssl.severity_score.authority_invalid" units="%">
   <obsolete>
     Deprecated Jan 2015 (M42).
@@ -61070,6 +61079,11 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="9" label="UNKNOWN"/>
 </enum>
 
+<enum name="SSLGoodCertSeenEvent" type="int">
+  <int value="0" label="NO_PREVIOUS_EXCEPTION"/>
+  <int value="1" label="HAD_PREVIOUS_EXCEPTION"/>
+</enum>
+
 <enum name="SSLIsExpiredAndDecision" type="int">
   <int value="0" label="EXPIRED_AND_PROCEED"/>
   <int value="1" label="EXPIRED_AND_DO_NOT_PROCEED"/>