Use output parameter to distinguish error from absent result

Use output parameter to distinguish error from absent result
Otherwise we'd have to probe for pending exceptions.

I'll do the same to other interceptors in follow-up CLs

BUG=chromium:495949,v8:4137
LOG=n

Review URL: https://codereview.chromium.org/1190023002

Cr-Commit-Position: refs/heads/master@{#29090}