Store Object.observe state per-isolate rather than per-context

test/cctest/cctest.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 61 matching lines @@
         'test-hashing.cc',
         'test-hashmap.cc',
         'test-heap.cc',
         'test-heap-profiler.cc',
         'test-list.cc',
         'test-liveedit.cc',
         'test-lock.cc',
         'test-lockers.cc',
         'test-log.cc',
         'test-mark-compact.cc',
+        'test-object-observe.cc',
         'test-parsing.cc',
         'test-platform-tls.cc',
         'test-profile-generator.cc',
         'test-random.cc',
         'test-regexp.cc',
         'test-reloc-info.cc',
         'test-serialize.cc',
         'test-sockets.cc',
         'test-spaces.cc',
         'test-strings.cc',
@@ skipping 100 matching lines @@
             '<@(_outputs)',
             'TEST',  # type
             'off',  # compression
             '<@(file_list)',
           ],
         }
       ],
     },
   ],
 }