[Autofill] Dedupe profiles on each major version.

components/autofill/core/common/autofill_pref_names.cc

Index: components/autofill/core/common/autofill_pref_names.cc
diff --git a/components/autofill/core/common/autofill_pref_names.cc b/components/autofill/core/common/autofill_pref_names.cc
index 20a98831591b3ee5f247f7e837b009610e84348a..526b93a063f0f8fe3816f4aca3acaf86b4ec59cd 100644
--- a/components/autofill/core/common/autofill_pref_names.cc
+++ b/components/autofill/core/common/autofill_pref_names.cc
@@ -18,6 +18,10 @@ const char kAutofillProfileUseDatesFixed[] = "autofill.profile_use_dates_fixed";
 // 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[] =