Refactor the samevalue internal method and add tests for this method....

src/runtime.js

Index: src/runtime.js
===================================================================
--- src/runtime.js	(revision 4711)
+++ src/runtime.js	(working copy)
@@ -559,19 +559,15 @@
 // ES5, section 9.12
 function SameValue(x, y) {
   if (typeof x != typeof y) return false;
-  if (IS_NULL_OR_UNDEFINED(x)) return true;
   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 && (1 / x) != (1 / y)) {
       return false;
     }
-    return x == y;
+    return x === y;
   }
-  if (IS_STRING(x)) return %StringEquals(x, y);
-  if (IS_BOOLEAN(x)) return y == x;
-
-  return %_ObjectEquals(x, y);
+  return x === y
 }