Fix return values for Harmony map and set operations.

src/collection.js

 // Copyright 2011 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 @@
 
 
 function SetDelete(key) {
   if (!IS_SET(this)) {
     throw MakeTypeError('incompatible_method_receiver',
                         ['Set.prototype.delete', this]);
   }
   if (IS_UNDEFINED(key)) {
     key = undefined_sentinel;
   }
-  return %SetDelete(this, key);
+  if (%SetHas(this, key)) {
+    %SetDelete(this, key);
+    return true;
+  } else {
+    return false;
+  }
 }
 
 
 function MapConstructor() {
   if (%_IsConstructCall()) {
     %MapInitialize(this);
   } else {
     return new $Map();
   }
 }
@@ skipping 148 matching lines @@
   %SetProperty($WeakMap.prototype, "constructor", $WeakMap, DONT_ENUM);
 
   // Set up the non-enumerable functions on the WeakMap prototype object.
   InstallFunctions($WeakMap.prototype, DONT_ENUM, $Array(
     "get", WeakMapGet,
     "set", WeakMapSet,
     "has", WeakMapHas,
     "delete", WeakMapDelete
   ));
 })();