Make base compile with no "using base::FilePath".

base/json/json_file_value_serializer.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.
 
 #ifndef BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
 #define BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_
 
 #include <string>
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/values.h"
 
 class BASE_EXPORT JSONFileValueSerializer : public base::ValueSerializer {
  public:
   // json_file_patch is the path of a file that will be source of the
   // deserialization or the destination of the serialization.
   // When deserializing, the file should exist, but when serializing, the
   // serializer will attempt to create the file at the specified location.
-  explicit JSONFileValueSerializer(const FilePath& json_file_path)
+  explicit JSONFileValueSerializer(const base::FilePath& json_file_path)
     : json_file_path_(json_file_path),
       allow_trailing_comma_(false) {}
 
   virtual ~JSONFileValueSerializer() {}
 
   // DO NOT USE except in unit tests to verify the file was written properly.
   // We should never serialize directly to a file since this will block the
   // thread. Instead, serialize to a string and write to the file you want on
   // the file thread.
   //
@@ skipping 35 matching lines @@
   // be a JsonFileError.
   static const char* GetErrorMessageForCode(int error_code);
 
   void set_allow_trailing_comma(bool new_value) {
     allow_trailing_comma_ = new_value;
   }
 
  private:
   bool SerializeInternal(const Value& root, bool omit_binary_values);
 
-  FilePath json_file_path_;
+  base::FilePath json_file_path_;
   bool allow_trailing_comma_;
 
   // A wrapper for file_util::ReadFileToString which returns a non-zero
   // JsonFileError if there were file errors.
   int ReadFileToString(std::string* json_string);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSONFileValueSerializer);
 };
 
 #endif  // BASE_JSON_JSON_FILE_VALUE_SERIALIZER_H_