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/audio/channel_send.cc b/audio/channel_send.cc
index 982d932..f38df24 100644
--- a/audio/channel_send.cc
+++ b/audio/channel_send.cc
@@ -17,7 +17,6 @@
 #include <utility>
 #include <vector>
 
-#include "absl/memory/memory.h"
 #include "api/array_view.h"
 #include "api/call/transport.h"
 #include "api/crypto/frame_encryptor_interface.h"
@@ -662,7 +661,7 @@
   _rtpRtcpModule = RtpRtcp::Create(configuration);
   _rtpRtcpModule->SetSendingMediaStatus(false);
 
-  rtp_sender_audio_ = absl::make_unique<RTPSenderAudio>(
+  rtp_sender_audio_ = std::make_unique<RTPSenderAudio>(
       configuration.clock, _rtpRtcpModule->RtpSender());
 
   // We want to invoke the 'TargetRateObserver' and |OnOverheadChanged|
@@ -1204,7 +1203,7 @@
     bool extmap_allow_mixed,
     int rtcp_report_interval_ms,
     uint32_t ssrc) {
-  return absl::make_unique<ChannelSend>(
+  return std::make_unique<ChannelSend>(
       clock, task_queue_factory, module_process_thread, media_transport_config,
       overhead_observer, rtp_transport, rtcp_rtt_stats, rtc_event_log,
       frame_encryptor, crypto_options, extmap_allow_mixed,