Update AutoImport to import nothing by default (in absence of policy and master_prefs).

chrome/browser/prefs/profile_pref_store_manager.cc

 // Copyright 2014 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/prefs/profile_pref_store_manager.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 152 matching lines @@
       base::Bind(&JsonPrefStore::RegisterOnNextSuccessfulWriteReply,
                  protected_pref_store->AsWeakPtr()),
       GetPrefHashStore(false), GetPrefHashStore(true),
       raw_unprotected_pref_hash_filter, raw_protected_pref_hash_filter);
 
   return new SegregatedPrefStore(unprotected_pref_store, protected_pref_store,
                                  protected_pref_names);
 }
 
 bool ProfilePrefStoreManager::InitializePrefsFromMasterPrefs(
-    const base::DictionaryValue& master_prefs) {
+    std::unique_ptr<base::DictionaryValue> master_prefs) {
   // Create the profile directory if it doesn't exist yet (very possible on
   // first run).
   if (!base::CreateDirectory(profile_path_))
     return false;
 
-  const base::DictionaryValue* to_serialize = &master_prefs;
-  std::unique_ptr<base::DictionaryValue> copy;
-
   if (kPlatformSupportsPreferenceTracking) {
-    copy.reset(master_prefs.DeepCopy());
-    to_serialize = copy.get();
     PrefHashFilter(GetPrefHashStore(false),
                    GetExternalVerificationPrefHashStorePair(),
                    tracking_configuration_, base::Closure(), NULL,
                    reporting_ids_count_, false)
-        .Initialize(copy.get());
+        .Initialize(master_prefs.get());
   }
 
   // This will write out to a single combined file which will be immediately
   // migrated to two files on load.
   JSONFileValueSerializer serializer(
       profile_path_.Append(chrome::kPreferencesFilename));
 
   // Call Serialize (which does IO) on the main thread, which would _normally_
   // be verboten. In this case however, we require this IO to synchronously
   // complete before Chrome can start (as master preferences seed the Local
   // State and Preferences files). This won't trip ThreadIORestrictions as they
   // won't have kicked in yet on the main thread.
-  bool success = serializer.Serialize(*to_serialize);
+  bool success = serializer.Serialize(*master_prefs);
 
   UMA_HISTOGRAM_BOOLEAN("Settings.InitializedFromMasterPrefs", success);
   return success;
 }
 
 std::unique_ptr<PrefHashStore> ProfilePrefStoreManager::GetPrefHashStore(
     bool use_super_mac) {
   DCHECK(kPlatformSupportsPreferenceTracking);
 
   return std::unique_ptr<PrefHashStore>(
@@ skipping 12 matching lines @@
           ? base::MakeUnique<RegistryHashStoreContentsWin>(
                 *g_preference_validation_registry_path_for_testing,
                 profile_path_.BaseName().LossyDisplayName())
           : base::MakeUnique<RegistryHashStoreContentsWin>(
                 BrowserDistribution::GetDistribution()->GetRegistryPath(),
                 profile_path_.BaseName().LossyDisplayName()));
 #else
   return std::make_pair(nullptr, nullptr);
 #endif
 }