Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/api/peerconnectioninterface_unittest.cc

Index: webrtc/api/peerconnectioninterface_unittest.cc
diff --git a/webrtc/api/peerconnectioninterface_unittest.cc b/webrtc/api/peerconnectioninterface_unittest.cc
index d8d05f6732744a34d5a93cd357db02dcd95a209c..e0d9038d5ae73d3d43b7f497bf095d9ef6ac61ed 100644
--- a/webrtc/api/peerconnectioninterface_unittest.cc
+++ b/webrtc/api/peerconnectioninterface_unittest.cc
@@ -1402,7 +1402,7 @@ TEST_F(PeerConnectionInterfaceTest, TestSendBinaryOnRtpDataChannel) {
   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)));
 }