first-inspector-code-load and multi-inspector-code-load are broken

[danleh]

On d8, jsc and SpiderMonkey js I get essentially a 0ms measurement for startup/worst/average since 510e017 (after git bisect).
See:

Running first-inspector-code-load:
    Startup: 5000
    Worst Case: 5000
    Average: 5000
    Score: 5000.000
    Wall time: 0:00.003
...
Running multi-inspector-code-load:
    Startup: 5000
    Worst Case: 5000
    Average: 5000
    Score: 5000.000
    Wall time: 0:00.003

@kmiller68 could you take a look, e.g., whether switching from DefaultBenchmark to AsyncBenchmark broke something?

[kmiller68]

Whoops #90 if you want to take a look.