Record UMA when googlezip proxies are removed from the proxy config.

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 7a26d3b2e6785cda654ae9297d2504155e8b8f18..3843702fd5add03f92a6b2ee3d2555b209079224 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -20172,6 +20172,15 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.PrefProxyConfig.GooglezipProxyRemovalResult"
+    enum="GooglezipProxyRemovalResult">
+  <owner>sclittle@chromium.org</owner>
+  <summary>
+    Records whether or not a *.googlezip.net Data Reduction Proxy was removed
+    from the effective proxy configuration when a proxy reconfiguration occurs.
+  </summary>
+</histogram>
+
 <histogram name="Net.Priority_High_Latency" units="milliseconds">
   <obsolete>
     Replaced by Net.Priority_High_Latency_b.
@@ -54433,6 +54442,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="5" label="UPGRADE_ERROR"/>
 </enum>
 
+<enum name="GooglezipProxyRemovalResult" type="int">
+  <int value="0" label="No *.googlezip.net proxies found"/>
+  <int value="1" label="At least one *.googlezip.net proxy found and removed"/>
+</enum>
+
 <enum name="GzipEncodingFixupResult" type="int">
   <int value="0" label="Gzip encoding left as-is"/>
   <int value="1" label="MIME type indicated GZIP content"/>