Reimplement devfs in dart. Implementation now writes to disk.

runtime/vm/vm_sources.gypi

 # Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This file contains all sources (vm and tests) for the dart virtual machine.
 # Unit test files need to have a '_test' suffix appended to the name.
 {
   'sources': [
     'allocation.cc',
     'allocation.h',
@@ skipping 142 matching lines @@
     'debugger_arm.cc',
     'debugger_arm64.cc',
     'debugger_dbc.cc',
     'debugger_ia32.cc',
     'debugger_mips.cc',
     'debugger_x64.cc',
     'deferred_objects.cc',
     'deferred_objects.h',
     'deopt_instructions.cc',
     'deopt_instructions.h',
-    'dev_fs.cc',
-    'dev_fs.h',
     'disassembler.cc',
     'disassembler.h',
     'disassembler_arm.cc',
     'disassembler_arm64.cc',
     'disassembler_dbc.cc',
     'disassembler_ia32.cc',
     'disassembler_mips.cc',
     'disassembler_test.cc',
     'disassembler_x64.cc',
     'double_conversion.cc',
@@ skipping 361 matching lines @@
     'visitor.h',
     'weak_code.cc',
     'weak_code.h',
     'weak_table.cc',
     'weak_table.h',
     'zone.cc',
     'zone.h',
     'zone_test.cc',
   ],
 }