Revert "PromiseThen should ignore non-function parameters."

test/mjsunit/es6/promises.js

 // Copyright 2013 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
@@ skipping 381 matching lines @@
     assertUnreachable,
     function(x) { assertAsync(x === 5, "then/reject") }
   )
   deferred.reject(5)
   assertAsyncRan()
 })();
 
 (function() {
   var deferred = Promise.defer()
   var p1 = deferred.promise
-  var p2 = p1.then(1, 2)
-  p2.then(
-    function(x) { assertAsync(x === 5, "then/resolve-non-function") },
-    assertUnreachable
-  )
-  deferred.resolve(5)
-  assertAsyncRan()
-})();
-
-(function() {
-  var deferred = Promise.defer()
-  var p1 = deferred.promise
-  var p2 = p1.then(1, 2)
-  p2.then(
-    assertUnreachable,
-    function(x) { assertAsync(x === 5, "then/reject-non-function") }
-  )
-  deferred.reject(5)
-  assertAsyncRan()
-})();
-
-(function() {
-  var deferred = Promise.defer()
-  var p1 = deferred.promise
   var p2 = {then: function(onResolve, onReject) { onResolve(p1) }}
   var p3 = Promise.accept(p2)
   p3.chain(
     function(x) { assertAsync(x === p2, "chain/resolve/thenable") },
     assertUnreachable
   )
   deferred.resolve(5)
   assertAsyncRan()
 })();
 
@@ skipping 380 matching lines @@
   Promise.all([11, Promise.accept(12), 13, MyPromise.accept(14), 15, 16])
   assertTrue(log === "nx14n", "subclass/all/arg")
 
   log = ""
   MyPromise.all([21, Promise.accept(22), 23, MyPromise.accept(24), 25, 26])
   assertTrue(log === "nx24nnx21nnx23nnnx25nnx26n", "subclass/all/self")
 })();
 
 
 assertAsyncDone()