Allow TranslateRanker to override decisions taken by heuristics.

components/metrics/proto/translate_event.proto

Index: components/metrics/proto/translate_event.proto
diff --git a/components/metrics/proto/translate_event.proto b/components/metrics/proto/translate_event.proto
index 94ae6ecb2ff167326c70dcd30767033506ed18ce..c403fd979fb705009f3177ae22f72d30bedbaf74 100644
--- a/components/metrics/proto/translate_event.proto
+++ b/components/metrics/proto/translate_event.proto
@@ -16,7 +16,7 @@ package metrics;
 // the Translate UI. Contains features used by Translate Ranker for
 // inference, information about the ranker model and its decision, as
 // well as user or automated feedback from the Translate UI.
-// Next tag: 15
+// Next tag: 16
 message TranslateEventProto {
   // Language strings are two or three letter codes, with sometimes an extra
   // suffix (for e.g. chinese zh-TW or zh-CN). See
@@ -136,6 +136,10 @@ message TranslateEventProto {
   // Event received from translate UI.
   optional EventType event_type = 10;
 
+  // Decisions that have been overriden by translate ranker (e.g.
+  // LANGUAGE_DISABLED_BY_AUTO_BLACKLIST).
+  repeated EventType decision_overrides = 15;
+
   // The timestamp for the event, in seconds.
   // This value comes from Chromium's TimeTicks::Now(), which is an abstract
   // time value that is guaranteed to always be increasing (regardless of