Skeleton for showing "Show all saved passwords row" for Linux/CrOs/Windows platforms

components/password_manager/core/common/password_manager_features.cc

Index: components/password_manager/core/common/password_manager_features.cc
diff --git a/components/password_manager/core/common/password_manager_features.cc b/components/password_manager/core/common/password_manager_features.cc
index 5dce1e7eba2e0c43a4eb3f0a003303966235c753..342c2e0f06d6d5f4953a75ec5e7a948c4281f863 100644
--- a/components/password_manager/core/common/password_manager_features.cc
+++ b/components/password_manager/core/common/password_manager_features.cc
@@ -18,6 +18,11 @@ const base::Feature kAffiliationBasedMatching = {
 const base::Feature kDropSyncCredential = {"drop-sync-credential",
                                            base::FEATURE_ENABLED_BY_DEFAULT};
 
+// Enable additional elements in the form popup UI, which will allow the user to
+// trigger generation or view all saved passwords.
+const base::Feature kEnableManualFallbacksFilling = {
+    "EnableManualFallbacksFilling", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enable a context menu item in the password field that allows the user
 // to manually enforce saving of their password.
 const base::Feature kEnablePasswordForceSaving = {