[builtins] Drop useless ToBoolean JavaScript builtin.

src/runtime.js

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This files contains runtime support implemented in JavaScript.
 
 // CAUTION: Some of the functions specified in this file are called
 // directly from compiled code. These are the functions with names in
 // ALL CAPS. The compiled code passes the first argument in 'this'.
 
@@ skipping 148 matching lines @@
 function CONCAT_ITERABLE_TO_ARRAY(iterable) {
   return %concat_iterable_to_array(this, iterable);
 };
 
 
 /* -------------------------------------
    - - -   C o n v e r s i o n s   - - -
    -------------------------------------
 */
 
-// ECMA-262, section 9.2, page 30
-function ToBoolean(x) {
-  if (IS_BOOLEAN(x)) return x;
-  if (IS_STRING(x)) return x.length != 0;
-  if (x == null) return false;
-  if (IS_NUMBER(x)) return !((x == 0) || NUMBER_IS_NAN(x));
-  return true;
-}
-
-
 // ES5, section 9.12
 function SameValue(x, y) {
   if (typeof x != typeof y) return false;
   if (IS_NUMBER(x)) {
     if (NUMBER_IS_NAN(x) && NUMBER_IS_NAN(y)) return true;
     // x is +0 and y is -0 or vice versa.
     if (x === 0 && y === 0 && %_IsMinusZero(x) != %_IsMinusZero(y)) {
       return false;
     }
   }
@@ skipping 26 matching lines @@
    - - -   U t i l i t i e s   - - -
    ---------------------------------
 */
 
 
 // ES6, draft 10-14-14, section 22.1.3.1.1
 function IsConcatSpreadable(O) {
   if (!IS_SPEC_OBJECT(O)) return false;
   var spreadable = O[isConcatSpreadableSymbol];
   if (IS_UNDEFINED(spreadable)) return IS_ARRAY(O);
-  return ToBoolean(spreadable);
+  return TO_BOOLEAN(spreadable);
 }
 
 
 function ToPositiveInteger(x, rangeErrorIndex) {
   var i = TO_INTEGER_MAP_MINUS_ZERO(x);
   if (i < 0) throw MakeRangeError(rangeErrorIndex);
   return i;
 }
 
 //----------------------------------------------------------------------------
@@ skipping 17 matching lines @@
   "apply_prepare_builtin", APPLY_PREPARE,
   "concat_iterable_to_array_builtin", CONCAT_ITERABLE_TO_ARRAY,
   "reflect_apply_prepare_builtin", REFLECT_APPLY_PREPARE,
   "reflect_construct_prepare_builtin", REFLECT_CONSTRUCT_PREPARE,
 ]);
 
 %InstallToContext([
   "concat_iterable_to_array", ConcatIterableToArray,
 ]);
 
-utils.Export(function(to) {
-  to.ToBoolean = ToBoolean;
-});
-
 })