[api] Assume that v8/include is in the include path for all public headers

tools/gyp/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 1870 matching lines @@
         '../../src/libplatform/worker-thread.cc',
         '../../src/libplatform/worker-thread.h',
       ],
       'conditions': [
         ['want_separate_host_toolset==1', {
           'toolsets': ['host', 'target'],
         }, {
           'toolsets': ['target'],
         }],
       ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          '../../include',
+        ],
+      },
     },
     {
       'target_name': 'natives_blob',
       'type': 'none',
       'conditions': [
         [ 'v8_use_external_startup_data==1', {
           'conditions': [
             ['want_separate_host_toolset==1', {
               'dependencies': ['js2c#host'],
             }, {
@@ skipping 303 matching lines @@
         }],
         ['want_separate_host_toolset==1', {
           'toolsets': ['host'],
         }, {
           'toolsets': ['target'],
         }],
       ],
     },
   ],
 }