Add a country field to TranslateEventProto.

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 8bba508af402815bfa53938ad5a4be8fc4907fd5..94ae6ecb2ff167326c70dcd30767033506ed18ce 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: 14
+// Next tag: 15
 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
@@ -27,6 +27,10 @@ message TranslateEventProto {
   // Target language of the translation.
   optional string target_language = 2;
 
+  // The country where the user is. 2-letter country code. This
+  // corresponds to the stored permanent country in VariationsService.
+  optional string country = 14;
+
   // The following counts are extracted from TranslatePrefs.
   // The number of times the user accepted a translation for the
   // source language.