"API replacement summary:
- AccountTrackerService::SeedAccountInfo => IdentityTestEnvironment or identity_test_utils to make account available
"

For ios WebView, it doesn't expect that UpdateCredentials is called at
https://cs.chromium.org/chromium/src/components/signin/ios/browser/profile_oauth2_token_service_ios_delegate.mm?q=profile_oauth2_token_service_ios_delegate&sq=package:chromium&g=0&l=256.

AFIK, we don't have API only for SeedAccountInfo() in IdentityTestEnvironment or identity_test_utils.

So, I'll wait for IdentityManager::LegacySeedAccountInfo at  crbug.com/922473 .
If there is anything I missed, please let me know.

Now we can use LegacySeedAccountInfo instead of SeedAccountInfo but we need to remove the dependency of ProfileOAuth2TokenService in order to move cwv_sync_controller_unittest.mm away from using AccountTrackerService.

So, I added the issue, crbug.com/913927, to 'Blocked on' field.