Replace base::NullableString16(bool) usage with default constructor.

webkit/browser/dom_storage/session_storage_database.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 "webkit/browser/dom_storage/session_storage_database.h"
 
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 505 matching lines @@
   // Skip the dummy entry "map-<mapid>-".
   for (it->Next(); it->Valid(); it->Next()) {
     std::string key = it->key().ToString();
     if (key.find(map_start_key) != 0) {
       // Iterated past the keys in this map.
       break;
     }
     // Key is of the form "map-<mapid>-<key>".
     base::string16 key16 = UTF8ToUTF16(key.substr(map_start_key.length()));
     if (only_keys) {
-      (*result)[key16] = base::NullableString16(true);
+      (*result)[key16] = base::NullableString16();
     } else {
       // Convert the raw data stored in std::string (it->value()) to raw data
       // stored in base::string16.
       size_t len = it->value().size() / sizeof(char16);
       const char16* data_ptr =
           reinterpret_cast<const char16*>(it->value().data());
       (*result)[key16] =
           base::NullableString16(base::string16(data_ptr, len), false);
     }
   }
@@ skipping 130 matching lines @@
 std::string SessionStorageDatabase::MapKey(const std::string& map_id,
                                            const std::string& key) {
   return base::StringPrintf("map-%s-%s", map_id.c_str(), key.c_str());
 }
 
 const char* SessionStorageDatabase::NextMapIdKey() {
   return "next-map-id";
 }
 
 }  // namespace dom_storage