Enable new feature flag needed for butter sync.

A new flag was added recently that prevented server cards from being
offered as autofill suggestions. We simply enable to restore the
intended behavior.

Change-Id: I537ae79a6bf6acfef081f9002654e4d4fc202fe5
Reviewed-on: https://chromium-review.googlesource.com/c/1371202
Commit-Queue: John Wu <jzw@chromium.org>
Reviewed-by: Hiroshi Ichikawa <ichikawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615438}

ios/web_view/internal/web_view_web_main_parts.mm

@@ -48,6 +48,7 @@ void WebViewWebMainParts::PreCreateThreads() {
   std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
   std::string enable_features = base::JoinString(
       {autofill::features::kAutofillEnableAccountWalletStorage.name,
+       autofill::features::kAutofillAlwaysShowServerCardsInSyncTransport.name,
        switches::kSyncStandaloneTransport.name,
        switches::kSyncSupportSecondaryAccount.name,
        switches::kSyncUSSAutofillWalletData.name},