Extensions: Add metrics for Web Request API actions.

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 159b46d2ad2720fab193c188119815146780173e..eca6db9bee60468fed8758baa1fdf1ce8aff56a8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -18941,6 +18941,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Updates grouped by Extension::HistogramType.</summary>
 </histogram>
 
+<histogram name="Extensions.WebRequestAction" enum="WebRequestAction">
+  <owner>karandeepb@chromium.org</owner>
+  <summary>
+    Describes the action taken by the Web Request Extension API for a given
+    stage of a web request.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.WebRequestEventFoundFrame" units="boolean">
   <owner>rdevlin.cronin@chromium.org</owner>
   <summary>
@@ -110373,6 +110381,16 @@ value.
   <int value="2" label="WEB_HISTORY_QUERY_TIMED_OUT">Timed out</int>
 </enum>
 
+<enum name="WebRequestAction" type="int">
+  <int value="0" label="CANCEL"/>
+  <int value="1" label="REDIRECT"/>
+  <int value="2" label="MODIFY_REQUEST_HEADERS"/>
+  <int value="3" label="MODIFY_REQUEST_COOKIES"/>
+  <int value="4" label="MODIFY_RESPONSE_HEADERS"/>
+  <int value="5" label="MODIFY_RESPONSE_COOKIES"/>
+  <int value="6" label="SET_AUTH_CREDENTIALS"/>
+</enum>
+
 <enum name="WebRtcAudioCodecs" type="int">
   <int value="0" label="Unknown"/>
   <int value="1" label="Opus"/>