Stop password migration from the Keychain on Mac.

components/password_manager/core/browser/keychain_migration_status_mac.h

Index: components/password_manager/core/browser/keychain_migration_status_mac.h
diff --git a/components/password_manager/core/browser/keychain_migration_status_mac.h b/components/password_manager/core/browser/keychain_migration_status_mac.h
index 70f25f246c64958620d154f097cb25433c65c0af..7260a6aaf47a293dde5b0ffe364e7ca6b9f90671 100644
--- a/components/password_manager/core/browser/keychain_migration_status_mac.h
+++ b/components/password_manager/core/browser/keychain_migration_status_mac.h
@@ -29,6 +29,10 @@ enum class MigrationStatus {
   // Best effort migration happened. Some passwords were inaccessible.
   MIGRATED_PARTIALLY,
 
+  // Gave up on migration as the passwords aren't accessible anyway after Chrome
+  // changes the certificate.

[jdoerrie, 2017/03/02 17:02:28]

Could you add a link providing more information how and when this exactly
happens?

+  MIGRATION_STOPPED,
+
   MIGRATION_STATUS_COUNT,
 };