Add UMA for recording embargo reasons and autoblocker interactions.

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 75942790af4f363c40aeb5a680d3589d150b3942..dca18eeb81b2e40634fd2fc02260b146f3fa52cd 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -45984,6 +45984,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Permissions.AutoBlocker.EmbargoReason"
+    enum="PermissionEmbargoReason">
+  <owner>dominickn@chromium.org</owner>
+  <owner>kcarattini@chromium.org</owner>
+  <summary>
+    Tracks the reason that an (origin, permission) pair has been placed under
+    embargo (blocked from making requests for that permission for a period of
+    time).
+  </summary>
+</histogram>
+
 <histogram name="Permissions.Prompt.Accepted" enum="PermissionRequestType">
   <owner>dominickn@chromium.org</owner>
   <owner>kcarattini@chromium.org</owner>
@@ -102125,6 +102136,12 @@ value.
   <int value="4" label="REVOKED"/>
 </enum>
 
+<enum name="PermissionEmbargoReason" type="int">
+  <int value="0" label="NOT_EMBARGOED"/>
+  <int value="1" label="BLACKLISTED"/>
+  <int value="2" label="REPEATED_DISMISSALS"/>
+</enum>
+
 <enum name="PermissionRequestType" type="int">
   <int value="0" label="PERMISSION_BUBBLE_UNKNOWN"/>
   <int value="1" label="PERMISSION_BUBBLE_MULTIPLE"/>