Use std::make_unique instead of absl::make_unique.

WebRTC is now using C++14 so there is no need to use the Abseil version
of std::make_unique.

This CL has been created with the following steps:

git grep -l absl::make_unique | sort | uniq > /tmp/make_unique.txt
git grep -l absl::WrapUnique | sort | uniq > /tmp/wrap_unique.txt
git grep -l "#include <memory>" | sort | uniq > /tmp/memory.txt

diff --new-line-format="" --unchanged-line-format="" \
  /tmp/make_unique.txt /tmp/wrap_unique.txt | sort | \
  uniq > /tmp/only_make_unique.txt
diff --new-line-format="" --unchanged-line-format="" \
  /tmp/only_make_unique.txt /tmp/memory.txt | \
  xargs grep -l "absl/memory" > /tmp/add-memory.txt

git grep -l "\babsl::make_unique\b" | \
  xargs sed -i "s/\babsl::make_unique\b/std::make_unique/g"

git checkout PRESUBMIT.py abseil-in-webrtc.md

cat /tmp/add-memory.txt | \
  xargs sed -i \
  's/#include "absl\/memory\/memory.h"/#include <memory>/g'
git cl format
# Manual fix order of the new inserted #include <memory>

cat /tmp/only_make_unique | xargs grep -l "#include <memory>" | \
  xargs sed -i '/#include "absl\/memory\/memory.h"/d'

git ls-files | grep BUILD.gn | \
  xargs sed -i '/\/\/third_party\/abseil-cpp\/absl\/memory/d'

python tools_webrtc/gn_check_autofix.py \
  -m tryserver.webrtc -b linux_rel

# Repead the gn_check_autofix step for other platforms

git ls-files | grep BUILD.gn | \
  xargs sed -i 's/absl\/memory:memory/absl\/memory/g'
git cl format

Bug: webrtc:10945
Change-Id: I3fe28ea80f4dd3ba3cf28effd151d5e1f19aff89
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/153221
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Alessio Bazzica <alessiob@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29209}
diff --git a/pc/peer_connection_rtp_unittest.cc b/pc/peer_connection_rtp_unittest.cc
index 67aa98d..b709992 100644
--- a/pc/peer_connection_rtp_unittest.cc
+++ b/pc/peer_connection_rtp_unittest.cc
@@ -15,7 +15,6 @@
 #include <utility>
 #include <vector>
 
-#include "absl/memory/memory.h"
 #include "absl/types/optional.h"
 #include "api/audio/audio_mixer.h"
 #include "api/audio_codecs/audio_decoder_factory.h"
@@ -138,13 +137,13 @@
   // adjustment.
   std::unique_ptr<PeerConnectionWrapper> CreatePeerConnectionInternal(
       const RTCConfiguration& config) {
-    auto observer = absl::make_unique<MockPeerConnectionObserver>();
+    auto observer = std::make_unique<MockPeerConnectionObserver>();
     auto pc = pc_factory_->CreatePeerConnection(config, nullptr, nullptr,
                                                 observer.get());
     EXPECT_TRUE(pc.get());
     observer->SetPeerConnectionInterface(pc.get());
-    return absl::make_unique<PeerConnectionWrapper>(pc_factory_, pc,
-                                                    std::move(observer));
+    return std::make_unique<PeerConnectionWrapper>(pc_factory_, pc,
+                                                   std::move(observer));
   }
 };