Now that SuspendGenerator returns, we have to update the interrupt
budget during that return to ensure that generators can be optimized.

Bug: chromium:804796
Change-Id: I8a9fa1c2399da81a3c2a7d8a07a774d5648d1c5e
Reviewed-on: https://chromium-review.googlesource.com/880821Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50796}