Update from https://crrev.com/307330

net/quic/crypto/chacha20_poly1305_decrypter_test.cc

 // Copyright 2014 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/crypto/chacha20_poly1305_decrypter.h"
 
 #include "net/quic/test_tools/quic_test_utils.h"
 
 using base::StringPiece;
+using std::string;
 
 namespace {
 
 // The test vectors come from draft-agl-tls-chacha20poly1305-04 Section 7.
 
 // Each test vector consists of six strings of lowercase hexadecimal digits.
 // The strings may be empty (zero length). A test vector with a NULL |key|
 // marks the end of an array of test vectors.
 struct TestVector {
   // Input:
@@ skipping 103 matching lines @@
     EXPECT_TRUE(has_pt);
 
     ASSERT_EQ(pt.length(), decrypted->length());
     test::CompareCharArraysWithHexError("plaintext", decrypted->data(),
                                         pt.length(), pt.data(), pt.length());
   }
 }
 
 }  // namespace test
 }  // namespace net