ScriptPromiseResolver leaked resource when constructed on stopped context.

ScriptPromiseResolver stops working when the associated ExecutionContext is
stopped. ScriptPromiseResolver can be constructed on a stopped
ExecutionContext. In such a case the constructed resolver is stopped as well.
Moreover, it should release the created (internal) resolver not to leak
resource.

BUG=385384

Review URL: https://codereview.chromium.org/622733002

git-svn-id: svn://svn.chromium.org/blink/trunk@183123 bbb929c8-8fbe-4397-9dbb-9b2b20218538