This adds a regression test for a bug where {OsrPoll} instructions
within the bytecode stream ended up outside of actual loops. This has
been fixed already, by merging {OsrPoll} into the backwards branch.
R=rmcilroy@chromium.org
TEST=mjsunit/regress/regress-crbug-645888
BUG=chromium:645888
Review-Url: https://codereview.chromium.org/2337033002
Cr-Commit-Position: refs/heads/master@{#39385}
