Re-enable Object.observe and add enforcement for security invariants.

test/mjsunit/mjsunit.status

 # 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
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@@ skipping 109 matching lines @@
   'regress/regress-336820': [PASS, FAIL],
 
   # BUG(v8:2989). PASS/FAIL on linux32 because crankshaft is turned off for
   # nosse2. Also for arm novfp3.
   'regress/regress-2989': [FAIL, NO_VARIANTS, ['system == linux and arch == ia32 or arch == arm and simulator == True', PASS]],
 
   # Skip endain dependent test for mips due to different typed views of the same
   # array buffer.
   'nans': [PASS, ['arch == mips', SKIP]],
 
-  # Object.observe is disabled.
-  'es6/promises': [SKIP],
-  'array-push7': [SKIP],
-  'harmony/microtask-delivery': [SKIP],
-  'es7/object-observe': [SKIP],
-  'harmony/regress/regress-observe-empty-double-array': [SKIP],
-  'regress/regress-356589': [SKIP],
-  'regress/regress-observe-map-cache': [SKIP],
 }],  # ALWAYS
 
 ##############################################################################
 ['gc_stress == True', {
   # Skip tests not suitable for GC stress.
   'allocation-site-info': [SKIP],
   'array-constructor-feedback': [SKIP],
   'array-feedback': [SKIP],
   'array-literal-feedback': [SKIP],
   'd8-performance-now': [SKIP],
@@ skipping 250 matching lines @@
   'never-optimize': [SKIP],
   'regress/regress-2185-2': [SKIP],
   'harmony/object-observe': [SKIP],
   'readonly': [SKIP],
   'array-feedback': [SKIP],
 
   # Deopt every n garbage collections collides with deopt every n times.
   'regress/regress-2653': [SKIP],
 }],  # 'deopt_fuzzer == True'
 ]