This makes sure we are not inserting {OsrPoll} instructions for any
statements that are not actually loops and have no back edges. Without
back edges the {BytecodeGraphBuilder} is unable to deduce loop ranges
and hence cannot construct a graph for OSR entry.

R=neis@chromium.org
TEST=mjsunit/regress/regress-5252
BUG=v8:5252

Review-Url: https://codereview.chromium.org/2200733002
Cr-Commit-Position: refs/heads/master@{#38233}