Add histogram for key exchange strength

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 27455195e5988d3c44c62bad96bcef30c0a5c9a7..fc1c49e6264c7558eb2249070c62b2f14e513a44 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -24614,6 +24614,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Net.SSL_KeyExchange">
+  <owner>sigbjorn@opera.com</owner>
+  <owner>agl@chromium.org</owner>
+  <owner>rsleevi@chromium.org</owner>
+  <summary>
+    Key exchange information/strength, by connection method. Recorded for each
+    SSL/TLS connection in the socket pool where Connect() succeeds.
+  </summary>
+</histogram>
+
 <histogram name="Net.SSLCertBlacklisted">
   <owner>agl@chromium.org</owner>
   <summary>
@@ -75420,6 +75430,23 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Net.QuicSession.PacketReceived_Nack"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="Net.SSL_KeyExchange_subsections" separator=".">
+  <owner>sigbjorn@opera.com</owner>
+  <owner>agl@chromium.org</owner>
+  <owner>rsleevi@chromium.org</owner>
+  <suffix name="DH" label="DH"/>
+  <suffix name="DHE" label="DHE"/>
+  <suffix name="RSA" label="RSA"/>
+  <suffix name="ECDH" label="ECDH"/>
+  <suffix name="ECDHE" label="ECDHE"/>
+  <suffix name="Unknown" label="Unknown"/>
+  <summary>
+    Key exchange information/strength, by connection method. Recorded for each
+    SSL/TLS connection in the socket pool where Connect() succeeds.
+  </summary>
+  <affected-histogram name="Net.SSL_KeyExchange"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="NetConnectivity" separator=".">
   <suffix name="53.100B" label="100 bytes of data on port 53."/>
   <suffix name="53.100B.NoProxy"