New heap always reported as full even if it is not

[B3rn475]

The new heap is always reported to be full by the Scavenger.

Run script:

import 'dart:async' show Timer, Duration;

final waste = [];

void topLevel(period) {
  new Timer.periodic(period, (Timer t) {
    waste.add(new List.filled(10000, 5));
  });
}

main() {
  topLevel(const Duration(seconds: 1));
}

Open Observatory in the Allocation Profile page

[dnunez02]

The new space uses top_ to determine how many words the new space is using. However, that information is in the mutator thread local state now.

I will update the appropriate functions to use the proper data.

[dnunez02]

https://codereview.chromium.org/2992153002/