After this cl: https://chromium-review.googlesource.com/c/508668/
the decisions on inlining polymorphic functions are done per
function. This regresses Octane/raytrace. Tuning the inlining 
heuristics to fix the regression.

Bug: chromium:724924
Change-Id: I027563de84723e4e39af4de49f85507468b96af3
Reviewed-on: https://chromium-review.googlesource.com/509554Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45474}