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/media_session_unittest.cc b/pc/media_session_unittest.cc
index a0d9d0c..e3778d6 100644
--- a/pc/media_session_unittest.cc
+++ b/pc/media_session_unittest.cc
@@ -485,7 +485,7 @@
     std::unique_ptr<SessionDescription> current_desc;
     std::unique_ptr<SessionDescription> desc;
     if (has_current_desc) {
-      current_desc = absl::make_unique<SessionDescription>();
+      current_desc = std::make_unique<SessionDescription>();
       current_desc->AddTransportInfo(TransportInfo(
           "audio",
           TransportDescription(current_audio_ufrag, current_audio_pwd)));
@@ -3283,7 +3283,7 @@
   cricket::ContentGroup group(cricket::CN_AUDIO);
   source.AddGroup(group);
   std::unique_ptr<AudioContentDescription> acd =
-      absl::make_unique<AudioContentDescription>();
+      std::make_unique<AudioContentDescription>();
   acd->set_codecs(MAKE_VECTOR(kAudioCodecs1));
   acd->AddLegacyStream(1);
   std::unique_ptr<AudioContentDescription> acd_passed =
@@ -3291,7 +3291,7 @@
   source.AddContent(cricket::CN_AUDIO, MediaProtocolType::kRtp,
                     std::move(acd_passed));
   std::unique_ptr<VideoContentDescription> vcd =
-      absl::make_unique<VideoContentDescription>();
+      std::make_unique<VideoContentDescription>();
   vcd->set_codecs(MAKE_VECTOR(kVideoCodecs1));
   vcd->AddLegacyStream(2);
   std::unique_ptr<VideoContentDescription> vcd_passed =