update_engine: migrate from base::MakeUnique to std::make_unique

base::MakeUnique is being deprecated as we can now use std::make_unique
when compiling code in the C++14 mode.

BUG=chromium:769107
CQ-DEPEND=CL:669672
TEST=Run unit tests.

Change-Id: I82f76647239b1eb3b98b19f6479788ffd86ce756
Reviewed-on: https://chromium-review.googlesource.com/716826
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/real_system_state.cc b/real_system_state.cc
index d1af41f..2a208ae 100644
--- a/real_system_state.cc
+++ b/real_system_state.cc
@@ -16,12 +16,12 @@
 
 #include "update_engine/real_system_state.h"
 
+#include <memory>
 #include <string>
 
 #include <base/bind.h>
 #include <base/files/file_util.h>
 #include <base/location.h>
-#include <base/memory/ptr_util.h>
 #include <base/time/time.h>
 #include <brillo/message_loops/message_loop.h>
 #if USE_CHROME_KIOSK_APP
@@ -56,7 +56,7 @@
   if (!boot_control_) {
     LOG(WARNING) << "Unable to create BootControl instance, using stub "
                  << "instead. All update attempts will fail.";
-    boot_control_ = base::MakeUnique<BootControlStub>();
+    boot_control_ = std::make_unique<BootControlStub>();
   }
 
   hardware_ = hardware::CreateHardware();