Fix compilation failure when v8 is compiled with Chromium using GYP.

src/v8.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 1984 matching lines @@
       'target_name': 'v8_libplatform',
       'type': 'static_library',
       'variables': {
         'optimize': 'max',
       },
       'dependencies': [
         'v8_libbase',
       ],
       'include_dirs+': [
         '..',
+        '<(DEPTH)',
         '../include',
       ],
       'sources': [
         '../include/libplatform/libplatform.h',
         '../include/libplatform/v8-tracing.h',
         'libplatform/default-platform.cc',
         'libplatform/default-platform.h',
         'libplatform/task-queue.cc',
         'libplatform/task-queue.h',
         'libplatform/tracing/trace-buffer.cc',
@@ skipping 370 matching lines @@
       'conditions': [
         ['want_separate_host_toolset_mkpeephole==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }