PasswordStore: Clean up expectations about rewriting vectors of forms

chrome/browser/password_manager/password_store_x.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/password_manager/password_store_x.h"
 
 #include <algorithm>
 #include <map>
 #include <vector>
 
@@ skipping 128 matching lines @@
 ScopedVector<autofill::PasswordForm> PasswordStoreX::FillMatchingLogins(
     const autofill::PasswordForm& form,
     AuthorizationPromptPolicy prompt_policy) {
   CheckMigration();
   ScopedVector<autofill::PasswordForm> matched_forms;
   if (use_native_backend() && backend_->GetLogins(form, &matched_forms)) {
     SortLoginsByOrigin(&matched_forms.get());
     // The native backend may succeed and return no data even while locked, if
     // the query did not match anything stored. So we continue to allow fallback
     // until we perform a write operation, or until a read returns actual data.
-    if (matched_forms.size() > 0)
+    if (!matched_forms.empty())
       allow_fallback_ = false;
-  } else if (allow_default_store()) {
-    DCHECK(matched_forms.empty());
+    return matched_forms.Pass();
+  }
+  if (allow_default_store())
     return PasswordStoreDefault::FillMatchingLogins(form, prompt_policy);
-  }
-  return matched_forms.Pass();
+  return ScopedVector<autofill::PasswordForm>();
 }
 
 bool PasswordStoreX::FillAutofillableLogins(
     ScopedVector<autofill::PasswordForm>* forms) {
+  forms->clear();
   CheckMigration();
   if (use_native_backend() && backend_->GetAutofillableLogins(forms)) {
     SortLoginsByOrigin(&forms->get());
     // See GetLoginsImpl() for why we disallow fallback conditionally here.
     if (!forms->empty())
       allow_fallback_ = false;
     return true;
   }
   if (allow_default_store())
     return PasswordStoreDefault::FillAutofillableLogins(forms);
   return false;
 }
 
 bool PasswordStoreX::FillBlacklistLogins(
     ScopedVector<autofill::PasswordForm>* forms) {
+  forms->clear();
   CheckMigration();
   if (use_native_backend() && backend_->GetBlacklistLogins(forms)) {
     // See GetLoginsImpl() for why we disallow fallback conditionally here.
     SortLoginsByOrigin(&forms->get());
     if (!forms->empty())
       allow_fallback_ = false;
     return true;
   }
   if (allow_default_store())
     return PasswordStoreDefault::FillBlacklistLogins(forms);
@@ skipping 29 matching lines @@
     backend_.reset();
     // Don't warn again. We'll use the default store because backend_ is NULL.
     allow_fallback_ = false;
   }
   return !backend_.get();
 }
 
 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
     // don't somehow end up with some of the passwords in one store and some in
     // another. We'll always have at least one intact store this way.
     for (size_t i = 0; i < forms.size(); ++i) {
       PasswordStoreChangeList changes;
       if (!AddLoginToBackend(backend_, *forms[i], &changes)) {
         ok = false;
         break;
@@ skipping 12 matching lines @@
       // Finally, delete the database file itself. We remove the passwords from
       // it before deleting the file just in case there is some problem deleting
       // the file (e.g. directory is not writable, but file is), which would
       // otherwise cause passwords to re-migrate next (or maybe every) time.
       DeleteAndRecreateDatabaseFile();
     }
   }
   ssize_t result = ok ? forms.size() : -1;
   return result;
 }