[promises] Remove IsPromise

src/builtins/builtins-promise.cc

 // Copyright 2016 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.
 
 #include "src/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 
 #include "src/code-factory.h"
 #include "src/promise-utils.h"
 
@@ skipping 201 matching lines @@
   Node* const context = a.Parameter(3);
   Node* const native_context = a.LoadNativeContext(context);
   Node* const promise_fun =
       a.LoadContextElement(native_context, Context::PROMISE_FUNCTION_INDEX);
   Node* const initial_map =
       a.LoadObjectField(promise_fun, JSFunction::kPrototypeOrInitialMapOffset);
   Node* const instance = a.AllocateJSObjectFromMap(initial_map);
   a.Return(instance);
 }
 
-// TODO(gsathya): Refactor promise.js::IsPromise to use this.
 void Builtins::Generate_IsPromise(compiler::CodeAssemblerState* state) {
   CodeStubAssembler a(state);
   typedef compiler::Node Node;
   typedef CodeStubAssembler::Label Label;
 
   Node* const maybe_promise = a.Parameter(1);
   Label if_ispromise(&a), if_isnotpromise(&a, Label::kDeferred);
   a.GotoIf(a.TaggedIsSmi(maybe_promise), &if_isnotpromise);
 
   a.Branch(a.HasInstanceType(maybe_promise, JS_PROMISE_TYPE), &if_ispromise,
            &if_isnotpromise);
 
   a.Bind(&if_ispromise);
   a.Return(a.BooleanConstant(true));
 
   a.Bind(&if_isnotpromise);
   a.Return(a.BooleanConstant(false));
 }
 
 }  // namespace internal
 }  // namespace v8