Update the remaining include paths of base/string_piece.h to its new location.

crypto/hmac.h

 // 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.
 
 // Utility class for calculating the HMAC for a given message. We currently
 // only support SHA1 for the hash algorithm, but this can be extended easily.
 
 #ifndef CRYPTO_HMAC_H_
 #define CRYPTO_HMAC_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "crypto/crypto_export.h"
 
 namespace crypto {
 
 // Simplify the interface and reduce includes by abstracting out the internals.
 struct HMACPlatformData;
 class SymmetricKey;
 
 class CRYPTO_EXPORT HMAC {
  public:
@@ skipping 59 matching lines @@
  private:
   HashAlgorithm hash_alg_;
   scoped_ptr<HMACPlatformData> plat_;
 
   DISALLOW_COPY_AND_ASSIGN(HMAC);
 };
 
 }  // namespace crypto
 
 #endif  // CRYPTO_HMAC_H_