Set username-first-flow flag in automated tests

Test recipe capture_update_pass_nexon expects the username to be stored
on password update, which will only happen with new feature.

Updating test code to ensure the feature flag is set on test setup.

If it is preferred to not use this feature in the tests for now,
let me know and I will update the test recipe.

Bug: 959776
Change-Id: I306886fbb9daa0e434e5011ebd6aa80c1dfeac5e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1872732Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Commit-Queue: Ian Struiksma <ianstruiksma@google.com>
Auto-Submit: Ian Struiksma <ianstruiksma@google.com>
Cr-Commit-Position: refs/heads/master@{#708289}

chrome/browser/password_manager/password_manager_captured_sites_interactive_uitest.cc

@@ -17,6 +17,7 @@
 #include "chrome/browser/ui/tab_dialogs.h"
 #include "components/autofill/core/common/password_form.h"
 #include "components/password_manager/core/browser/test_password_store.h"
+#include "components/password_manager/core/common/password_manager_features.h"
 #include "content/public/test/test_utils.h"
 
 using captured_sites_test_utils::CapturedSiteParams;
@@ -173,6 +174,8 @@ class CapturedSitesPasswordManagerBrowserTest
   }
 
   void SetUpCommandLine(base::CommandLine* command_line) override {
+    feature_list_.InitWithFeatures(
+        /*enabled_features=*/{features::kUsernameFirstFlow}, {});
     InProcessBrowserTest::SetUpCommandLine(command_line);
     captured_sites_test_utils::TestRecipeReplayer::SetUpCommandLine(
         command_line);
@@ -204,6 +207,7 @@ class CapturedSitesPasswordManagerBrowserTest
  private:
   std::unique_ptr<captured_sites_test_utils::TestRecipeReplayer>
       recipe_replayer_;
+  base::test::ScopedFeatureList feature_list_;
   content::WebContents* web_contents_ = nullptr;
   std::unique_ptr<ServerUrlLoader> server_url_loader_;