[es6] Implement spec compliant ToPrimitive in the runtime.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index 1503373d4a3fc6c78cc2630b039800f30c338b08..1ef4e973fdc8dd1baff155916e15b1e75155cc88 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -11,7 +11,6 @@
 
 // The following declarations are shared with other native JS files.
 // They are all declared at this one spot to avoid redeclaration errors.
-var $defaultNumber;
 var $defaultString;
 var $NaN;
 var $nonNumberToNumber;
@@ -826,7 +825,6 @@ function ToPositiveInteger(x, rangeErrorIndex) {
 // ----------------------------------------------------------------------------
 // Exports
 
-$defaultNumber = DefaultNumber;
 $defaultString = DefaultString;
 $NaN = %GetRootNaN();
 $nonNumberToNumber = NonNumberToNumber;
@@ -880,7 +878,6 @@ $toString = ToString;
   "sub_builtin", SUB,
   "sub_strong_builtin", SUB_STRONG,
   "to_name_builtin", TO_NAME,
-  "to_number_builtin", TO_NUMBER,
   "to_string_builtin", TO_STRING,
 ]);