Set Token-Binding HTTP header

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 a7c5c2cfc3c7a1085e1463185dc0700045706d74..8f47872de46aef2c7661a52ce8c2d91ccfdd9244 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -27516,6 +27516,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Net.TokenBinding.Support" enum="TokenBinding.Support">
+  <owner>nharper@chromium.org</owner>
+  <summary>
+    Count of number of secure HTTP requests broken down by support for Token

[Mark P, 2016/01/23 05:01:49]

option nit: "Count of" -> "The"

[nharper, 2016/01/25 18:54:54]

Done.

+    Binding, indicating if Token Binding was negotiated and supported by both
+    client and server, or why it wasn't if not.
+  </summary>
+</histogram>
+
 <histogram name="Net.Transaction_Bandwidth" units="KB/s">
   <obsolete>
     Discontinued as of 4/12/09
@@ -79623,6 +79632,13 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="Renegotiation patched"/>
 </enum>
 
+<enum name="TokenBinding.Support" type="int">
+  <int value="0" label="DISABLED"/>
+  <int value="1" label="CLIENT_ONLY"/>
+  <int value="2" label="CLIENT_AND_SERVER"/>
+  <int value="3" label="CLIENT_NO_CHANNEL_ID_SERVICE"/>
+</enum>
+
 <enum name="TouchEventsState" type="int">
   <int value="0" label="Enabled"/>
   <int value="1" label="Automatic - enabled"/>