The "do I inline?" decision needs many of the same inputs as the "should
I even try to crankshaft?" decision.  This change consolidates these
checks in the numbering pass.  It also removes the is_generator() check,
as that's already handled when visiting the initial Yield expression.

R=svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/775693003

Cr-Commit-Position: refs/heads/master@{#25642}