Reland Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/api/peerconnectioninterface_unittest.cc

 /*
  *  Copyright 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 1382 matching lines @@
   EXPECT_EQ(DataChannelInterface::kConnecting, data1->state());
   EXPECT_EQ(DataChannelInterface::kConnecting, data2->state());
 
   CreateOfferReceiveAnswer();
   EXPECT_TRUE_WAIT(observer1->IsOpen(), kTimeout);
   EXPECT_TRUE_WAIT(observer2->IsOpen(), kTimeout);
 
   EXPECT_EQ(DataChannelInterface::kOpen, data1->state());
   EXPECT_EQ(DataChannelInterface::kOpen, data2->state());
 
-  rtc::Buffer buffer("test", 4);
+  rtc::CopyOnWriteBuffer buffer("test", 4);
   EXPECT_FALSE(data1->Send(DataBuffer(buffer, true)));
 }
 
 // This test setup a RTP data channels in loop back and test that a channel is
 // opened even if the remote end answer with a zero SSRC.
 TEST_F(PeerConnectionInterfaceTest, TestSendOnlyDataChannel) {
   FakeConstraints constraints;
   constraints.SetAllowRtpDataChannels();
   CreatePeerConnection(&constraints);
   scoped_refptr<DataChannelInterface> data1  =
@@ skipping 1269 matching lines @@
   FakeConstraints updated_answer_c;
   answer_c.SetMandatoryReceiveAudio(false);
   answer_c.SetMandatoryReceiveVideo(false);
 
   cricket::MediaSessionOptions updated_answer_options;
   EXPECT_TRUE(
       ParseConstraintsForAnswer(&updated_answer_c, &updated_answer_options));
   EXPECT_TRUE(updated_answer_options.has_audio());
   EXPECT_TRUE(updated_answer_options.has_video());
 }