For context, When Wallet syncs, all cards get replaced. Because of that, all their use_date were set to "now" at every sync.

Now Load the use stats from disk if possible.

Also for new Chromium instance where the is nothing on disk, added logic to keep use_date from metadata sync if the local version has never been used.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/109e10b0a48a1f09d242562611c2556b12a29da6

commit 109e10b0a48a1f09d242562611c2556b12a29da6
Author: sebsg <sebsg@chromium.org>
Date: Mon Mar 13 16:23:34 2017

[Autofill] Preserve use stats of existing Wallet cards when syncing.

Load the use stats from disk when saving Wallet Cards.

Add specific logic to overwrite a Wallet card use data in case the
metadata gets delayed. The previous logic was keep most recent which
resulted in making old card seem like they were just used.

BUG= 700486 

Review-Url: https://codereview.chromium.org/2741233002
Cr-Commit-Position: refs/heads/master@{#456395}

[modify] https://crrev.com/109e10b0a48a1f09d242562611c2556b12a29da6/components/autofill/core/browser/webdata/autofill_wallet_metadata_syncable_service.cc
[modify] https://crrev.com/109e10b0a48a1f09d242562611c2556b12a29da6/components/autofill/core/browser/webdata/autofill_wallet_metadata_syncable_service_unittest.cc
[modify] https://crrev.com/109e10b0a48a1f09d242562611c2556b12a29da6/components/autofill/core/browser/webdata/autofill_wallet_syncable_service.cc
[modify] https://crrev.com/109e10b0a48a1f09d242562611c2556b12a29da6/components/autofill/core/browser/webdata/autofill_wallet_syncable_service.h
[modify] https://crrev.com/109e10b0a48a1f09d242562611c2556b12a29da6/components/autofill/core/browser/webdata/autofill_wallet_syncable_service_unittest.cc

Your change meets the bar and is auto-approved for M58. Please go ahead and merge the CL to branch 3029 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), bhthompson@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18

commit c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18
Author: sebsg <sebsg@chromium.org>
Date: Mon Mar 20 19:26:40 2017

[Merge-58] Preserve use stats of existing Wallet cards when syncing.

Load the use stats from disk when saving Wallet Cards.

Add specific logic to overwrite a Wallet card use data in case the
metadata gets delayed. The previous logic was keep most recent which
resulted in making old card seem like they were just used.

BUG= 700486 

Review-Url: https://codereview.chromium.org/2741233002
Cr-Commit-Position: refs/heads/master@{#456395}
(cherry picked from commit 109e10b0a48a1f09d242562611c2556b12a29da6)

Review-Url: https://codereview.chromium.org/2759183003 .
Cr-Commit-Position: refs/branch-heads/3029@{#308}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}

[modify] https://crrev.com/c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18/components/autofill/core/browser/webdata/autofill_wallet_metadata_syncable_service.cc
[modify] https://crrev.com/c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18/components/autofill/core/browser/webdata/autofill_wallet_metadata_syncable_service_unittest.cc
[modify] https://crrev.com/c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18/components/autofill/core/browser/webdata/autofill_wallet_syncable_service.cc
[modify] https://crrev.com/c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18/components/autofill/core/browser/webdata/autofill_wallet_syncable_service.h
[modify] https://crrev.com/c558a4c40f4b3dd67cc6f50a879bc1f6e16fbe18/components/autofill/core/browser/webdata/autofill_wallet_syncable_service_unittest.cc