Update from https://crrev.com/307330

net/quic/quic_default_packet_writer.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_default_packet_writer.h"
 
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 
 namespace net {
 
 QuicDefaultPacketWriter::QuicDefaultPacketWriter() : weak_factory_(this) {
 }
 
 QuicDefaultPacketWriter::QuicDefaultPacketWriter(DatagramClientSocket* socket)
     : socket_(socket),
       write_blocked_(false),
       weak_factory_(this) {
 }
 
 QuicDefaultPacketWriter::~QuicDefaultPacketWriter() {}
 
 WriteResult QuicDefaultPacketWriter::WritePacket(
-    const char* buffer, size_t buf_len,
+    const char* buffer,
+    size_t buf_len,
     const net::IPAddressNumber& self_address,
     const net::IPEndPoint& peer_address) {
   scoped_refptr<StringIOBuffer> buf(
       new StringIOBuffer(std::string(buffer, buf_len)));
   DCHECK(!IsWriteBlocked());
+  base::TimeTicks now = base::TimeTicks::Now();
   int rv = socket_->Write(buf.get(),
                           buf_len,
                           base::Bind(&QuicDefaultPacketWriter::OnWriteComplete,
                                      weak_factory_.GetWeakPtr()));
   WriteStatus status = WRITE_STATUS_OK;
   if (rv < 0) {
     if (rv != ERR_IO_PENDING) {
       UMA_HISTOGRAM_SPARSE_SLOWLY("Net.QuicSession.WriteError", -rv);
       status = WRITE_STATUS_ERROR;
     } else {
       status = WRITE_STATUS_BLOCKED;
       write_blocked_ = true;
     }
   }
 
+  base::TimeDelta delta = base::TimeTicks::Now() - now;
+  if (status == WRITE_STATUS_OK) {
+    UMA_HISTOGRAM_TIMES("Net.QuicSession.PacketWriteTime.Synchronous", delta);
+  } else if (status == WRITE_STATUS_BLOCKED) {
+    UMA_HISTOGRAM_TIMES("Net.QuicSession.PacketWriteTime.Asynchronous", delta);
+  }
+
   return WriteResult(status, rv);
 }
 
 bool QuicDefaultPacketWriter::IsWriteBlockedDataBuffered() const {
   // Chrome sockets' Write() methods buffer the data until the Write is
   // permitted.
   return true;
 }
 
 bool QuicDefaultPacketWriter::IsWriteBlocked() const {
   return write_blocked_;
 }
 
 void QuicDefaultPacketWriter::SetWritable() {
   write_blocked_ = false;
 }
 
 void QuicDefaultPacketWriter::OnWriteComplete(int rv) {
   DCHECK_NE(rv, ERR_IO_PENDING);
   write_blocked_ = false;
   if (rv < 0) {
     connection_->OnWriteError(rv);
   }
   connection_->OnCanWrite();
 }
 
 }  // namespace net