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/payload_consumer/extent_writer_unittest.cc b/payload_consumer/extent_writer_unittest.cc
index 1f5fbaa..48b27cb 100644
--- a/payload_consumer/extent_writer_unittest.cc
+++ b/payload_consumer/extent_writer_unittest.cc
@@ -19,10 +19,10 @@
 #include <fcntl.h>
 
 #include <algorithm>
+#include <memory>
 #include <string>
 #include <vector>
 
-#include <base/memory/ptr_util.h>
 #include <brillo/secure_blob.h>
 #include <gtest/gtest.h>
 
@@ -159,7 +159,7 @@
   brillo::Blob data(kBlockSize * 2);
   test_utils::FillWithData(&data);
 
-  ZeroPadExtentWriter zero_pad_writer(base::MakeUnique<DirectExtentWriter>());
+  ZeroPadExtentWriter zero_pad_writer(std::make_unique<DirectExtentWriter>());
 
   EXPECT_TRUE(
       zero_pad_writer.Init(fd_, {extents.begin(), extents.end()}, kBlockSize));