Implement a 'trial parse' step, that will abort pre-parsing excessively
long and trivial functions, so that they can be eagerly compiled after all.
This essentially allows the parser to renege on its earlier decision to
lazy-parse, if additional information suggests it was a bad decision.

BUG=chromium:470930
LOG=Y

Review URL: https://codereview.chromium.org/1102523003

Cr-Commit-Position: refs/heads/master@{#28252}