Fix behavior of oneshot accessors of error objects.

test/mjsunit/error-accessors.js

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-// Flags: --allow-natives-syntax --expose-gc
+// Test that the oneshot accessors of error objects behave just like
+// data properties wrt objects that have the error object in the
+// prototype chain.
 
-DontEnum = 2;
+var o;
 
-var o = {};
-%SetProperty(o, "a", 0, DontEnum);
+// message is constructed as data property.
+var data_error = new Error("custom message");
+o = {};
+o.__proto__ = data_error;
 
-var o2 = {};
-%SetProperty(o2, "a", 0, DontEnum);
+assertEquals("custom message", o.message);
+o.message = "another message";
+assertEquals("another message", o.message);
+assertEquals("custom message", data_error.message);
 
-assertTrue(%HaveSameMap(o, o2));
+// message is constructed as getter.
+var getter_error_1;
+try { x.x } catch (e) { getter_error_1 = e; }
+o = {};
+o.__proto__ = getter_error_1;
 
-o.y = 2;
+assertEquals("x is not defined", o.message);  // Getter fires.
+o.message = "another message";
+assertEquals("another message", o.message);
+assertEquals("x is not defined", getter_error_1.message);
 
-for (var v in o) { print(v); }
+var getter_error_2;
+try { x.x } catch (e) { getter_error_2 = e; }
 o = {};
-gc();
+o.__proto__ = getter_error_2;
 
-for (var v in o2) { print(v); }
+o.message = "another message";  // Setter fires.
+assertEquals("another message", o.message);
+assertEquals("x is not defined", getter_error_1.message);