If the return_count is zero, the Generate will be called twice. The recent update in Generate function already handle the case inside the Generate function overload.

Change-Id: I49e0ee4a0824db60f157ea288ae6d28978c42db5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2215816Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68000}