[promises] Fix fast path in Promise.resolve

The receiver in the case of Promise.resolve is the promise
constructor, not an instance of Promise.

BUG=chromium:691875

Change-Id: I43e914aac51077b28c7954c8023780b9174df825
Reviewed-on: https://chromium-review.googlesource.com/450884Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43648}

src/builtins/builtins-promise.cc

@@ -1393,6 +1393,10 @@ TF_BUILTIN(PromiseResolve, PromiseBuiltinsAssembler) {
   ThrowIfNotJSReceiver(context, receiver, MessageTemplate::kCalledOnNonObject,
                        "PromiseResolve");
 
+  Node* const native_context = LoadNativeContext(context);
+  Node* const promise_fun =
+      LoadContextElement(native_context, Context::PROMISE_FUNCTION_INDEX);
+
   Label if_valueisnativepromise(this), if_valueisnotnativepromise(this),
       if_valueisnotpromise(this);
 
@@ -1404,9 +1408,6 @@ TF_BUILTIN(PromiseResolve, PromiseBuiltinsAssembler) {
 
   // This adds a fast path as non-subclassed native promises don't have
   // an observable constructor lookup.
-  Node* const native_context = LoadNativeContext(context);
-  Node* const promise_fun =
-      LoadContextElement(native_context, Context::PROMISE_FUNCTION_INDEX);
   BranchIfFastPath(native_context, promise_fun, value, &if_valueisnativepromise,
                    &if_valueisnotnativepromise);
 
@@ -1437,15 +1438,13 @@ TF_BUILTIN(PromiseResolve, PromiseBuiltinsAssembler) {
   Bind(&if_valueisnotpromise);
   {
     Label if_nativepromise(this), if_notnativepromise(this);
-    BranchIfFastPath(context, receiver, &if_nativepromise,
+    Branch(WordEqual(promise_fun, receiver), &if_nativepromise,
            &if_notnativepromise);
 
     // This adds a fast path for native promises that don't need to
     // create NewPromiseCapability.
     Bind(&if_nativepromise);
     {
-      Label do_resolve(this);
-
       Node* const result = AllocateAndInitJSPromise(context);
       InternalResolvePromise(context, result, value);
       Return(result);