Move StringPiece into the base namespace. It is colliding

base/data_pack.h

 // Copyright (c) 2008 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.
 
 // DataPack represents a read-only view onto an on-disk file that contains
 // (key, value) pairs of data.  It's used to store static resources like
 // translation strings and images.
 
 #ifndef BASE_DATA_PACK_H_
 #define BASE_DATA_PACK_H_
 
 #include "base/basictypes.h"
 #include "base/scoped_ptr.h"
 
 namespace file_util {
   class MemoryMappedFile;
 }
 class FilePath;
-class StringPiece;
 
 namespace base {
 
+class StringPiece;
+
 class DataPack {
  public:
   DataPack();
   ~DataPack();
 
   // Load a pack file from |path|, returning false on error.
   bool Load(const FilePath& path);
 
   // Get resource by id |resource_id|, filling in |data|.
   // The data is owned by the DataPack object and should not be modified.
   // Returns false if the resource id isn't found.
   bool Get(uint32_t resource_id, StringPiece* data);
 
  private:
   // The memory-mapped data.
   scoped_ptr<file_util::MemoryMappedFile> mmap_;
 
   // Number of resources in the data.
   size_t resource_count_;
 
   DISALLOW_COPY_AND_ASSIGN(DataPack);
 };
 
 }  // namespace base
 
 #endif  // BASE_DATA_PACK_H_