Review request for JDK-8037534

[Attila Szegedi]

Please review JDK-8037534 at http://cr.openjdk.java.net/~attila/8037534/webrev.00

From the JIRA issue: 

"When doing on-demand compilation, we can use the current runtime scope to look up types of variables in scope; if they're already wider than the current optimistic assumption, we can use that type and cut down on number of recompilation."

This cuts down warmup time with optimistic compilation. In Octane tests, box2d now does 1300 deoptimizations instead of 1552 while it warms up, and earley-boyer is down to 1577 from whopping 3028.

Thanks,
  Attila.