Query the existence other forms of browsing history.

sync/protocol/history_status.proto

Index: sync/protocol/history_status.proto
diff --git a/sync/protocol/history_status.proto b/sync/protocol/history_status.proto
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index 0000000000000000000000000000000000000000..e0f5ac9eaf27f81c388ed19fffc6047bb22faaa9
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+++ b/sync/protocol/history_status.proto
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+option retain_unknown_fields = true;
+
+package sync_pb;
+
+message HistoryStatusRequest {

[msramek, 2016/05/23 19:18:12]

After offline discussions with kevinliu@, I'm readding the request protobuf for
consistency, and explicitly serialize it to a string to be sent with the post
request (although I know that the result of the serialization is an empty
string).

+}
+
+// Response to a history status request.
+message HistoryStatusResponse {
+  // Minimal time to wait before issuing another request.
+  optional int32 min_poll_interval_seconds = 1 [default = 3600];
+
+  // Indicates whether the history corpuses have any derived data for a user.
+  optional bool has_derived_data = 2;
+}