The guard in JSFunction::MarkForOptimization checking whether a function
is being debugged is overly protective. The compilation pipeline will
bailout itself in that circumstance. Having the runtime behave similar
makes sure the debugger observes a situation closer to reality.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/1900743003

Cr-Commit-Position: refs/heads/master@{#35625}