Add a QUIC proxy server to the list of QUIC servers supported at start up

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 f88bbca1cdc651b8c4c1dc305195f6e397ead7fc..cbc88362212b00f850b1ee64863ad7d4c939821d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8664,6 +8664,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="DataReductionProxy.Quic.ProxyServerAtStartUpQueried"
+    enum="DataReductionProxyQuicProxyAtStartup">
+  <owner>tbansal@chromium.org</owner>
+  <owner>bengr@chromium.org</owner>
+  <summary>
+    Status of the availability of valid data reduction proxy servers that
+    support 0-RTT QUIC at startup. This metric is recorded only when data
+    reduction proxy delegate is queried for the list of supported QUIC proxy
+    servers.
+  </summary>
+</histogram>
+
 <histogram name="DataReductionProxy.Quic.ProxyStatus"
     enum="DataReductionProxyQuicProxyStatus">
   <owner>tbansal@chromium.org</owner>
@@ -77972,6 +77984,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="3" label="QUIC"/>
 </enum>
 
+<enum name="DataReductionProxyQuicProxyAtStartup" type="int">
+  <int value="0" label="QUIC proxy was available"/>
+  <int value="1" label="QUIC proxy was marked as broken"/>
+  <int value="2"
+      label="No supportable QUIC proxy was available in the list of data
+             reduction proxies"/>
+</enum>
+
 <enum name="DataReductionProxyQuicProxyStatus" type="int">
   <int value="0" label="QUIC proxy was available"/>
   <int value="1"