Fix bogus Object.isSealed check in some Array builtins.

src/array.js

Index: src/array.js
diff --git a/src/array.js b/src/array.js
index e23ecf3072e54799407cbdf2f80c25ceeeb8aeb9..2fa48b077a33c7a67f275028eb5fcbbf4726d660 100644
--- a/src/array.js
+++ b/src/array.js
@@ -463,10 +463,6 @@ function ArrayPush() {
 
   var n = TO_UINT32(this.length);
   var m = %_ArgumentsLength();
-  if (m > 0 && ObjectIsSealed(this)) {
-    throw MakeTypeError("array_functions_change_sealed",
-                        ["Array.prototype.push"]);
-  }
 
   if (%IsObserved(this))
     return ObservedArrayPush.apply(this, arguments);
@@ -649,11 +645,6 @@ function ArrayUnshift(arg1) {  // length == 1
   var num_arguments = %_ArgumentsLength();
   var is_sealed = ObjectIsSealed(this);
 
-  if (num_arguments > 0 && is_sealed) {
-    throw MakeTypeError("array_functions_change_sealed",
-                        ["Array.prototype.unshift"]);
-  }
-
   if (%IsObserved(this))
     return ObservedArrayUnshift.apply(this, arguments);