Simplify a string allocation and append into a single allocation

net/quic/test_tools/simple_quic_framer.cc

 // Copyright (c) 2012 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/test_tools/simple_quic_framer.h"
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 34 matching lines @@
   }
   void OnDecryptedPacket(EncryptionLevel level) override {}
   bool OnPacketHeader(const QuicPacketHeader& header) override {
     has_header_ = true;
     header_ = header;
     return true;
   }
 
   bool OnStreamFrame(const QuicStreamFrame& frame) override {
     // Save a copy of the data so it is valid after the packet is processed.
-    string* string_data = new string();
-    string_data->append(frame.data_buffer, frame.data_length);
+    string* string_data = new string(frame.data_buffer, frame.data_length);
     stream_data_.push_back(base::WrapUnique(string_data));
     // TODO(ianswett): A pointer isn't necessary with emplace_back.
     stream_frames_.push_back(base::MakeUnique<QuicStreamFrame>(
         frame.stream_id, frame.fin, frame.offset, StringPiece(*string_data)));
     return true;
   }
 
   bool OnAckFrame(const QuicAckFrame& frame) override {
     ack_frames_.push_back(frame);
     return true;
@@ skipping 161 matching lines @@
   return visitor_->goaway_frames();
 }
 
 const std::vector<QuicConnectionCloseFrame>&
 SimpleQuicFramer::connection_close_frames() const {
   return visitor_->connection_close_frames();
 }
 
 }  // namespace test
 }  // namespace net