Remove Error.prototype.toStrings prototype property.

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index b7e57aa228ea22f7db50da0fabb2aecd8445e5f7..3f73706ffa57732b876c060eaa0b09fe587f21b1 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -1059,8 +1059,8 @@ function errorToString() {
   }
 }
 
-%FunctionSetName(errorToString, 'toString');
-%SetProperty($Error.prototype, 'toString', errorToString, DONT_ENUM);
+
+InstallFunctions($Error.prototype, DONT_ENUM, ['toString', errorToString]);
 
 // Boilerplate for exceptions for stack overflows. Used from
 // Top::StackOverflow().