The optimization stages in the bytecode generation pipeline must
preserve source position information. Failure to preserve
source position information could result in single stepping
in the debugger misbehaving or mis-reporting in exception stack traces.

This change adds tests intended to check optimizations do not damage
source position info.

BUG=v8:4280
LOG=N

Review-Url: https://codereview.chromium.org/2042633002
Cr-Commit-Position: refs/heads/master@{#36855}