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

media/base/audio_hash.h

 // 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.
 
 #ifndef MEDIA_BASE_AUDIO_HASH_H_
 #define MEDIA_BASE_AUDIO_HASH_H_
 
 #include <string>
 
 #include "base/basictypes.h"
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 class AudioBus;
 
 // Computes a running hash for a series of AudioBus objects.  The hash is the
 // sum of each sample bucketed based on the frame index, channel number, and
 // current hash count.  The hash was designed with two properties in mind:
 //
@@ skipping 28 matching lines @@
   // The total number of samples processed per channel.  Uses a uint32 instead
   // of size_t so overflows on 64-bit and 32-bit machines are equivalent.
   uint32 sample_count_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioHash);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_HASH_H_