Use ExceptionState when converting string arguments to promise methods

A method whose return type is Promise should never throw an exception
directly, instead it should return a rejected promise holding the
exception that would have been thrown.

Because of this, string arguments in such methods were converted using a
special macro that extracted the exception from the v8::TryCatch local.

Since we want to get rid of that v8::TryCatch local, and also have a
V8StringResource::prepare() overload that reports exceptions via an
ExceptionState argument, use that for the method-returning-Promise case.

BUG=413257

Review URL: https://codereview.chromium.org/604833002

git-svn-id: svn://svn.chromium.org/blink/trunk@182687 bbb929c8-8fbe-4397-9dbb-9b2b20218538