The IteratorClose spec specifies that exceptions in
%GetMethod(iterator.return) are not suppressed by exceptions in the
given continuation (body of a loop, assignments in destructuring),
while exceptions in the execution of iterator.return() are.

This means that we have to split out the property access + a typeof
check to be outside the try-catch, and keep the call inside of it.

The non-split version is only for cases when there is no 'throws'
continuation (as is the case for yield* calling IteratorClose), so
the existing BuildIteratorClose can be renamed to reflect this.

Change-Id: Id71aea4fddd6ffb986bd9aaa09d29615a8800f71
Reviewed-on: https://chromium-review.googlesource.com/c/1402789Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58694}