[Sync] Add history delete directive type

sync/protocol/history_delete_directive_specifics.proto

+// Copyright (c) 2012 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.
+//
+// Sync protocol datatype extension for history delete directives.
+
+// Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
+// any fields in this file.
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+option retain_unknown_fields = true;
+
+package sync_pb;
+
+// All timestamps below are from Sane Time (
+// http://www.chromium.org/developers/design-documents/sane-time )
+// and are in microseconds since the Unix epoch.
+
+// Properties of history delete directive sync objects.
+message HistoryDeleteDirectiveSpecifics {
+  // Exactly one of the fields below must be filled in.  Otherwise, this
+  // delete directive must be ignored.
+  optional GlobalIdDirective global_id_directive = 1;
+  optional TimeRangeDirective time_range_directive = 2;
+  optional EverythingDirective everything_directive = 3;
+}
+
+message GlobalIdDirective {
+  // The global IDs of the navigations to delete.
+  repeated int64 global_id = 1;
+}
+
+message TimeRangeDirective {
+  // Both fields below must be filled in.  Otherwise, this delete directive
+  // must be ignored.
+
+  // The time on or after which entries must be deleted.
+  optional int64 start_time_usec = 1;
+  // The time on or before which entries must be deleted.
+  optional int64 end_time_usec = 2;
+}
+
+message EverythingDirective {
+  // The field below must be filled in and set to true.  Otherwise, this
+  // delete directive must be ignored.
+  optional bool delete_everything = 3 [default = false];

[Nicolas Zea, 2012/10/15 19:03:57]

does this need a timestamp? Otherwise a client might receive this well after the
event has passed, and delete too much right? Although in that case, we could
just reuse the above directive and have start_time_usec == 0 right?

[akalin, 2012/10/15 20:21:21]

We'd have to make it so that the client keeps track of the directives it's acted
upon, right.

But yeah, I guess we should make 'delete everything' be a time range, just to be
save.  Removed.

+}