[Autofill] Dedupe profiles on each major version.

components/autofill/core/common/autofill_pref_names.cc

 // Copyright 2013 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.
 
 #include "components/autofill/core/common/autofill_pref_names.h"
 
 namespace autofill {
 namespace prefs {
 
 // Boolean that is true if Autofill is enabled and allowed to save profile data.
 const char kAutofillEnabled[] = "autofill.enabled";
 
 // Boolean that is true if Autofill address profiles were fixed regarding their
 // bad use dates.
 const char kAutofillProfileUseDatesFixed[] = "autofill.profile_use_dates_fixed";
 
 // Boolean that's true when Wallet card and address import is enabled by the
 // user.
 const char kAutofillWalletImportEnabled[] = "autofill.wallet_import_enabled";
 
+// Integer that is set to the last version where the profile deduping routine
+// was run. This routine will be run once per version.
+const char kAutofillLastVersionDeduped[] = "autofill.last_version_deduped";
+
 // Boolean that allows the "Don't ask again for this card" checkbox to be
 // sticky.
 const char kAutofillWalletImportStorageCheckboxState[] =
     "autofill.wallet_import_storage_checkbox_state";
 
 }  // namespace prefs
 }  // namespace autofill