Add QuicStringPiece which is actually StringPiece.

net/tools/quic/chlo_extractor_test.cc

 // Copyright (c) 2016 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/tools/quic/chlo_extractor.h"
 
 #include "net/quic/core/quic_framer.h"
 #include "net/quic/test_tools/crypto_test_utils.h"
 #include "net/quic/test_tools/quic_test_utils.h"
 
-using base::StringPiece;
 using std::string;
 using testing::Return;
 using testing::_;
 
 namespace net {
 namespace test {
 namespace {
 
 class TestDelegate : public ChloExtractor::Delegate {
  public:
@@ skipping 103 matching lines @@
 
 TEST_F(ChloExtractorTest, DoesNotFindInvalidChlo) {
   MakePacket(new QuicStreamFrame(kCryptoStreamId, false, 0, "foo"));
   EXPECT_FALSE(
       ChloExtractor::Extract(*packet_, AllSupportedVersions(), &delegate_));
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace net