Move FileDescriptorShuffle to base/posix. This file is very posix-specific.

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 14460d4eecbefb7e80e9426be1c7d95882fac889..0497c1485898f12ca25fb57343b393f4d2dbc704 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -217,8 +217,6 @@
         'event_recorder.h',
         'event_recorder_stubs.cc',
         'event_recorder_win.cc',
-        'file_descriptor_shuffle.cc',
-        'file_descriptor_shuffle.h',
         'linux_util.cc',
         'linux_util.h',
         'md5.cc',
@@ -238,6 +236,8 @@
         'message_pump_mac.mm',
         'metrics/field_trial.cc',
         'metrics/field_trial.h',
+        'posix/file_descriptor_shuffle.cc',
+        'posix/file_descriptor_shuffle.h',
         'sync_socket.h',
         'sync_socket_win.cc',
         'sync_socket_posix.cc',
@@ -427,7 +427,6 @@
         'debug/trace_event_unittest.h',
         'debug/trace_event_win_unittest.cc',
         'environment_unittest.cc',
-        'file_descriptor_shuffle_unittest.cc',
         'file_path_unittest.cc',
         'file_util_proxy_unittest.cc',
         'file_util_unittest.cc',
@@ -493,6 +492,7 @@
         'path_service_unittest.cc',
         'pickle_unittest.cc',
         'platform_file_unittest.cc',
+        'posix/file_descriptor_shuffle_unittest.cc',
         'pr_time_unittest.cc',
         'process_util_unittest.cc',
         'process_util_unittest_ios.cc',