Promise.resolve

Instead of creating resolve and reject closures, directly
call ResolvePromise after creating the promise.

Using the following as a microbenchmark --
```
var b = 0;
var start = performance.now();
for (var i = 0; i < 1000000; i++) {
  Promise.resolve(1).then((val) => {
    b += val;
    if (b == 1000000) print(performance.now() - start)
  });
}
```

I see a 16.01% improvement over 5 runs with this patch.

BUG=v8:5046

Review-Url: https://codereview.chromium.org/2143553002
Cr-Commit-Position: refs/heads/master@{#38318}