Remove unnecessary %UnwrapGlobalProxy calls from object-observe.js

src/object-observe.js

 // 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 62 matching lines @@
   return observationState;
 }
 
 function GetWeakMapWrapper() {
   function MapWrapper(map) {
     this.map_ = map;
   };
 
   MapWrapper.prototype = {
     get: function(key) {
-      key = %UnwrapGlobalProxy(key);
-      if (!IS_SPEC_OBJECT(key)) return UNDEFINED;
       return %WeakCollectionGet(this.map_, key);
     },
     set: function(key, value) {
-      key = %UnwrapGlobalProxy(key);
-      if (!IS_SPEC_OBJECT(key)) return UNDEFINED;
       %WeakCollectionSet(this.map_, key, value);
     },
     has: function(key) {
       return !IS_UNDEFINED(this.get(key));
     }
   };
 
   return MapWrapper;
 }
 
@@ skipping 544 matching lines @@
     "observe", ArrayObserve,
     "unobserve", ArrayUnobserve
   ));
   InstallFunctions(notifierPrototype, DONT_ENUM, $Array(
     "notify", ObjectNotifierNotify,
     "performChange", ObjectNotifierPerformChange
   ));
 }
 
 SetupObjectObserve();