Add a missing DebugPromiseEvent in promise.js

DevTools expects 2 events on Promise.resolve()/Promise.reject():
creation & settlement. The first one was missing.

R=ulan@chromium.org, yangguo@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/792383003

Cr-Commit-Position: refs/heads/master@{#25778}