[WebView Autofill] Support all formless form

Support autofill all formless form by disable feature kAutofillRestrictUnownedFieldsToFormlessCheckout.

Bug: 816949
Change-Id: Ic5640f78ea97a956c37ccc6c86c2ca09242869d1
Reviewed-on: https://chromium-review.googlesource.com/939641Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539744}

android_webview/lib/aw_main_delegate.cc

@@ -173,6 +173,10 @@ bool AwMainDelegate::BasicStartupComplete(int* exit_code) {
   CommandLineHelper::AddEnabledFeature(
       *cl, autofill::features::kAutofillSkipComparingInferredLabels.name);
 
+  CommandLineHelper::AddDisabledFeature(
+      *cl, autofill::features::kAutofillRestrictUnownedFieldsToFormlessCheckout
+               .name);
+
   android_webview::RegisterPathProvider();
 
   safe_browsing_api_handler_.reset(