Implemented String.prototype.repeat as per ES6 draft 07-15-13, section 15.5.3.21

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index 92ac1bc46aac4a8e525b34accca62980848b6e92..436e0fc338b8c6049d1b99a82002dad2106bc0c6 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -126,6 +126,8 @@ var kMessages = {
 
   stack_overflow:                ["Maximum call stack size exceeded"],
   invalid_time_value:            ["Invalid time value"],
+
+  invalid_count_value:           ["Invalid count value"],
   // SyntaxError
   paren_in_arg_string:           ["Function arg string contains parenthesis"],
   not_isvar:                     ["builtin %IS_VAR: not a variable"],
@@ -1181,7 +1183,7 @@ function SetUpError() {
     // Store the error function in both the global object
     // and the runtime object. The function is fetched
     // from the runtime object when throwing errors from
-    // within the runtime system to avoid strange side
+    // within the runtime system to avoid stack side
     // effects when overwriting the error functions from
     // user code.
     var name = f.name;