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

src/objects.h

 // 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 855 matching lines @@
   V(PolymorphicCodeCacheHashTable)             \
   V(MapCache)                                  \
   V(Primitive)                                 \
   V(GlobalObject)                              \
   V(JSGlobalObject)                            \
   V(JSBuiltinsObject)                          \
   V(JSGlobalProxy)                             \
   V(UndetectableObject)                        \
   V(AccessCheckNeeded)                         \
   V(JSGlobalPropertyCell)                      \
+  V(ObjectHashTable)                           \
 
 
 class JSReceiver;
 
 // Object is the abstract superclass for all classes in the
 // object hierarchy.
 // Object does not use any virtual functions to avoid the
 // allocation of the C++ vtable.
 // Since Smi and Failure are subclasses of Object no
 // data members can be present in Object.
@@ skipping 8089 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_