Remove support for Object.observe

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 156 matching lines @@
   V(FixedArray, natives_source_cache, NativesSourceCache)                      \
   V(FixedArray, experimental_natives_source_cache,                             \
     ExperimentalNativesSourceCache)                                            \
   V(FixedArray, extra_natives_source_cache, ExtraNativesSourceCache)           \
   V(FixedArray, experimental_extra_natives_source_cache,                       \
     ExperimentalExtraNativesSourceCache)                                       \
   V(Script, empty_script, EmptyScript)                                         \
   V(NameDictionary, intrinsic_function_names, IntrinsicFunctionNames)          \
   V(NameDictionary, empty_properties_dictionary, EmptyPropertiesDictionary)    \
   V(Cell, undefined_cell, UndefinedCell)                                       \
-  V(JSObject, observation_state, ObservationState)                             \
   V(Object, symbol_registry, SymbolRegistry)                                   \
   V(Object, script_list, ScriptList)                                           \
   V(SeededNumberDictionary, empty_slow_element_dictionary,                     \
     EmptySlowElementDictionary)                                                \
   V(FixedArray, materialized_objects, MaterializedObjects)                     \
   V(FixedArray, microtask_queue, MicrotaskQueue)                               \
   V(TypeFeedbackVector, dummy_vector, DummyVector)                             \
   V(FixedArray, cleared_optimized_code_map, ClearedOptimizedCodeMap)           \
   V(FixedArray, detached_contexts, DetachedContexts)                           \
   V(ArrayList, retained_maps, RetainedMaps)                                    \
@@ skipping 2462 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_