PasswordStore: Clean up expectations about rewriting vectors of forms

chrome/browser/password_manager/password_store_x.cc

Index: chrome/browser/password_manager/password_store_x.cc
diff --git a/chrome/browser/password_manager/password_store_x.cc b/chrome/browser/password_manager/password_store_x.cc
index 595770f599d5d222c47aca3eed0661fdd58341bf..9cd6ca985e9424ad5dc08263ce2f125bfe2b9702 100644
--- a/chrome/browser/password_manager/password_store_x.cc
+++ b/chrome/browser/password_manager/password_store_x.cc
@@ -257,8 +257,12 @@ bool PasswordStoreX::allow_default_store() {
 ssize_t PasswordStoreX::MigrateLogins() {
   DCHECK(backend_.get());
   ScopedVector<autofill::PasswordForm> forms;
+  ScopedVector<autofill::PasswordForm> blacklist_forms;
   bool ok = PasswordStoreDefault::FillAutofillableLogins(&forms) &&
-      PasswordStoreDefault::FillBlacklistLogins(&forms);
+            PasswordStoreDefault::FillBlacklistLogins(&blacklist_forms);
+  forms.reserve(forms.size() + blacklist_forms.size());
+  forms.insert(forms.end(), blacklist_forms.begin(), blacklist_forms.end());
+  blacklist_forms.weak_clear();
   if (ok) {
     // We add all the passwords (and blacklist entries) to the native backend
     // before attempting to remove any from the login database, to make sure we