Function-granularity coverage skips functions that are both uncovered
and have an uncovered parent. This optimization needs to be tweaked once
block coverage and incremental collection is in play, as it is possible
to have a function with invocation_count == 0 (i.e. uncovered at
function granularity) that still has relevant block-granularity
coverage.

Bug: v8:6000
Change-Id: I4cc81b8a6935aa58e29d383ed4fa749cbfe69352
Reviewed-on: https://chromium-review.googlesource.com/589508Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46991}