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 4a165171b1e9e377c04615d56438fcbe639e67c9..e5cee740de576c6eec4236a3e13e15b883d0261d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -19295,6 +19295,15 @@ 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="RequestAction">
+  <owner>karandeepb@chromium.org</owner>
+  <summary>
+    Counts the number of times an action is requested by extensions as part of
+    the Web Request API. For a given web request stage, multiple actions may be
+    logged.
+  </summary>
+</histogram>
+
 <histogram name="Extensions.WebRequestEventFoundFrame" units="boolean">
   <owner>rdevlin.cronin@chromium.org</owner>
   <summary>
@@ -105663,6 +105672,14 @@ value.
   </int>
 </enum>
 
+<enum name="RequestAction" type="int">
+  <int value="0" label="CANCEL"/>
+  <int value="1" label="REDIRECT"/>
+  <int value="2" label="MODIFY_REQUEST_HEADERS"/>
+  <int value="3" label="MODIFY_RESPONSE_HEADERS"/>
+  <int value="4" label="SET_AUTH_CREDENTIALS"/>
+</enum>
+
 <enum name="RequestedImageMimeType" type="int">
   <int value="0" label="Png"/>
   <int value="1" label="Jpeg"/>