[runtime] Remove useless IN builtin.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index f7c91d3cc20e4130c4c6b20c46fe1c94483de68c..25825d78131935a43c94a234d6c400e0c29f85c9 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -44,7 +44,6 @@ var SAR;
 var SAR_STRONG;
 var SHR;
 var SHR_STRONG;
-var IN;
 var INSTANCE_OF;
 var CALL_NON_FUNCTION;
 var CALL_NON_FUNCTION_AS_CONSTRUCTOR;
@@ -483,21 +482,6 @@ SHR_STRONG = function SHR_STRONG(y) {
    -----------------------------
 */
 
-// ECMA-262, section 11.8.7, page 54.
-IN = function IN(x) {
-  if (!IS_SPEC_OBJECT(x)) {
-    throw %MakeTypeError(kInvalidInOperatorUse, this, x);
-  }
-  if (%_IsNonNegativeSmi(this)) {
-    if (IS_ARRAY(x) && %_HasFastPackedElements(x)) {
-      return this < x.length;
-    }
-    return %HasElement(x, this);
-  }
-  return %HasProperty(x, %$toName(this));
-}
-
-
 // ECMA-262, section 11.8.6, page 54. To make the implementation more
 // efficient, the return value should be zero if the 'this' is an
 // instance of F, and non-zero if not. This makes it possible to avoid