Add Locking calls to file_io.h plus implementations and test

util/util.gyp

 # Copyright 2014 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 254 matching lines @@
         '../compat/compat.gyp:crashpad_compat',
         '../third_party/gmock/gmock.gyp:gmock',
         '../third_party/gmock/gmock.gyp:gmock_main',
         '../third_party/gtest/gtest.gyp:gtest',
         '../third_party/mini_chromium/mini_chromium.gyp:base',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
+        'file/file_io_test.cc',
         'file/string_file_test.cc',
         'mac/checked_mach_address_range_test.cc',
         'mac/launchd_test.mm',
         'mac/mac_util_test.mm',
         'mac/service_management_test.mm',
         'mac/xattr_test.cc',
         'mach/child_port_handshake_test.cc',
         'mach/child_port_server_test.cc',
         'mach/composite_mach_message_server_test.cc',
         'mach/exc_client_variants_test.cc',
@@ skipping 100 matching lines @@
                 '/FIXED',
               ],
               'TargetMachine': '1',  # x86.
             },
           },
         },
       ]
     }],
   ],
 }