Rather than finalizing after rewriting do-expressions, we rewrite in the
outer scope if the block scope was finalized. Rewriting do expressions
cannot introduce any new nodes that requires the block to stay around,
so finalizing before and after is equivalent. (Only a temporary is
introduced which always ends up in a ClosureScope)

BUG=v8:5209
R=rossberg@chromium.org, caitpotter88@gmail.com, adamk@chromium.org

Review-Url: https://codereview.chromium.org/2167713004
Cr-Commit-Position: refs/heads/master@{#38193}