[AF Wallet] Fix non_unique_name for sync-internals

This CL fixes a minor bug in the implementation of
AutofillWalletSyncBridge::GetAllDataForDebugging() (which is only used
by chrome://sync-internals). After this patch, non_unique_name of the
entity data is a valid utf-8 string.

Bug: 853688
Change-Id: If80e2381654f90f8f3716668b585ab4deb7f9f1f
Reviewed-on: https://chromium-review.googlesource.com/c/1408909
Commit-Queue: Jan Krcal <jkrcal@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622831}
2 files changed