Roll metrics proto changes from internal

Bug: 996516
Change-Id: Ib3d3320d3a108a6c6b456092161308b3d2c566a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1820018
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Auto-Submit: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#699118}

third_party/metrics_proto/README.chromium

 Name: Metrics Protos
 Short Name: metrics_proto
 URL: This is the canonical public repository
-Version: 267295422
-Date: 2019/09/05 UTC
+Version: 270770521
+Date: 2019/09/23 UTC
 License: BSD
 Security Critical: Yes
 

third_party/metrics_proto/omnibox_event.proto

@@ -206,6 +206,8 @@ message OmniboxEventProto {
     // Non personalized query suggestions generated from a lightweight on device
     // head model.
     ON_DEVICE_HEAD = 17;
+    // Zero-prefix query suggestions based on device local history.
+    ZERO_SUGGEST_LOCAL_HISTORY = 18;
   }
 
   // The result set displayed on the completion popup