[builtins] Support SameValue and SameValueZero via runtime functions.

test/mjsunit/harmony/simd.js

 // Copyright 2015 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.
 
 // Flags: --harmony-simd --harmony-tostring  --harmony-reflect
 // Flags: --allow-natives-syntax --expose-natives-as natives --noalways-opt
 
 function lanesForType(typeName) {
   // The lane count follows the first 'x' in the type name, which begins with
   // 'float', 'int', or 'bool'.
@@ skipping 389 matching lines @@
       test(false, true);
       break;
   }
 }
 
 
 function TestSameValue(type, lanes) {
   var simdFn = SIMD[type];
   var instance = createInstance(type);
   var sameValue = Object.is
-  var sameValueZero = natives.ImportNow("SameValueZero");
+  var sameValueZero = function(x, y) { return %SameValueZero(x, y); }
 
   // SIMD values should not be the same as instances of different types.
   checkTypeMatrix(type, function(other) {
     assertFalse(sameValue(instance, other));
     assertFalse(sameValueZero(instance, other));
   });
 
   // Test that f(a, b) is the same as f(SIMD(a), SIMD(b)) for sameValue and
   // sameValueZero, at every lane.
   function test(a, b) {
@@ skipping 204 matching lines @@
   assertEquals(expected, JSON.stringify(input, null, 0));
 }
 
 TestStringify(undefined, SIMD.Float32x4(1, 2, 3, 4));
 TestStringify('[null]', [SIMD.Float32x4(1, 2, 3, 4)]);
 TestStringify('[{}]', [Object(SIMD.Float32x4(1, 2, 3, 4))]);
 var simd_wrapper = Object(SIMD.Float32x4(1, 2, 3, 4));
 TestStringify('{}', simd_wrapper);
 simd_wrapper.a = 1;
 TestStringify('{"a":1}', simd_wrapper);