[es6] Function bind should preserve [[Prototype]]

test/mjsunit/function-bind.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+// Flags: --allow-natives-syntax
+
 // Tests the Function.prototype.bind (ES 15.3.4.5) method.
 
 // Simple tests.
 function foo(x, y, z) {
   return [this, arguments.length, x];
 }
 
 assertEquals(3, foo.length);
 
 var f = foo.bind(foo);
@@ skipping 253 matching lines @@
 
 assertThrows(function() { return f.caller; }, TypeError);
 assertThrows(function() { f.caller = 42; }, TypeError);
 assertThrows(function() { return f.arguments; }, TypeError);
 assertThrows(function() { f.arguments = 42; }, TypeError);
 
 // Shouldn't throw. Accessing the functions caller must throw if
 // the caller is strict and the callee isn't. A bound function is built-in,
 // but not considered strict.
 (function foo() { return foo.caller; }).bind()();
+
+
+(function TestProtoIsPreserved() {
+  function fun() {}
+
+  function proto() {}
+  Object.setPrototypeOf(fun, proto);
+  var bound = fun.bind({});
+  assertEquals(proto, Object.getPrototypeOf(bound));
+
+  var bound2 = fun.bind({});
+  assertTrue(%HaveSameMap(new bound, new bound2));
+
+  Object.setPrototypeOf(fun, null);
+  bound = Function.prototype.bind.call(fun, {});
+  assertEquals(null, Object.getPrototypeOf(bound));
+})();