Cleanup how a best fit function is found when setting a breakpoint.
Cleanup how a best fit function is found when setting a breakpoint.

1. Look for functions/closures only in the script where the breakpoint
is being set.
2. If an inner most closure is found, return that as the best fit.
3. When going over a class' functions, return immediately when a fit is
found as going over the other class functions will not yield a narrower
fit.

BUG=
R=asiva@google.com

Review-Url: https://codereview.chromium.org/2898153006 .

dart-archive/dart-sdk,dart-lang/sdk,dart-lang/sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk