Add MakeUnique from chromium and change StunMessage::AddAttribute to take a unique_ptr.

webrtc/base/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/crypto.gni")
 import("//build/config/ui.gni")
@@ skipping 120 matching lines @@
     "onetimeevent.h",
     "optional.cc",
     "optional.h",
     "pathutils.cc",
     "pathutils.h",
     "platform_file.cc",
     "platform_file.h",
     "platform_thread.cc",
     "platform_thread.h",
     "platform_thread_types.h",
+    "ptr_util.h",
     "race_checker.cc",
     "race_checker.h",
     "random.cc",
     "random.h",
     "rate_limiter.cc",
     "rate_limiter.h",
     "rate_statistics.cc",
     "rate_statistics.h",
     "ratetracker.cc",
     "ratetracker.h",
@@ skipping 691 matching lines @@
       "httpcommon_unittest.cc",
       "httpserver_unittest.cc",
       "ipaddress_unittest.cc",
       "memory_usage_unittest.cc",
       "messagedigest_unittest.cc",
       "messagequeue_unittest.cc",
       "nat_unittest.cc",
       "network_unittest.cc",
       "optionsfile_unittest.cc",
       "proxy_unittest.cc",
+      "ptr_util_unittest.cc",
       "ratelimiter_unittest.cc",
       "rollingaccumulator_unittest.cc",
       "rtccertificate_unittest.cc",
       "rtccertificategenerator_unittest.cc",
       "scopedptrcollection_unittest.cc",
       "sha1digest_unittest.cc",
       "sharedexclusivelock_unittest.cc",
       "signalthread_unittest.cc",
       "sigslot_unittest.cc",
       "sigslottester_unittest.cc",
@@ skipping 33 matching lines @@
 
 if (is_android) {
   android_library("base_java") {
     java_files = [
       "java/src/org/webrtc/Logging.java",
       "java/src/org/webrtc/Size.java",
       "java/src/org/webrtc/ThreadUtils.java",
     ]
   }
 }