typesafe call-on-main-thread interface. no cast to/from void* required.

src/trusted/weak_ref/weak_ref.gyp

 # -*- python -*-
 # Copyright 2011 (c) The Native Client Authors. All rights reserved.  Use
 # of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 {
   'includes': [
     '../../../build/common.gypi',
   ],
   'target_defaults': {
     'variables':{
       'target_base': 'none',
     },
     'target_conditions': [
       ['target_base=="weak_ref"', {
         'sources': [
           'weak_ref.cc',
           'weak_ref.h',
+          'call_on_main_thread.h',
         ],
         'xcode_settings': {
           'WARNING_CFLAGS': [
             '-Wno-missing-field-initializers'
           ]
         },
       },
     ]],
   },
   'conditions': [
@@ skipping 42 matching lines @@
       'type': 'static_library', # 'dynamic_library', ?!?
       'variables': {
         'target_base': 'weak_ref',
       },
       'dependencies': [
         '<(DEPTH)/native_client/src/shared/platform/platform.gyp:platform',
       ],
     },
   ],
 }