.

src/debug/mirrors.js

Index: src/debug/mirrors.js
diff --git a/src/debug/mirrors.js b/src/debug/mirrors.js
index 1b45b93d8d77208e16375d3c94dafa1031dd3cfd..5368163a43091be44fedbae54375aa98e06d4add 100644
--- a/src/debug/mirrors.js
+++ b/src/debug/mirrors.js
@@ -8,6 +8,7 @@
 // ----------------------------------------------------------------------------
 // Imports
 
+var ErrorToString;
 var FunctionSourceString;
 var GlobalArray = global.Array;
 var IsNaN = global.isNaN;
@@ -19,6 +20,7 @@ var ToBoolean;
 var ToString;
 
 utils.Import(function(from) {
+  ErrorToString = from.ErrorToString;
   FunctionSourceString = from.FunctionSourceString;
   ToBoolean = from.ToBoolean;
   ToString = from.ToString;