Scanner cleanups: use isolates to allocate handles and zone objects

Scanner cleanups: use isolates to allocate handles and zone objects; remove C-heap allocation of structs.

R=hausner@google.com

Committed: https://code.google.com/p/dart/source/detail?r=37053

[hausner, 2014-06-05 21:58:54]

LGTM with one rant.

https://codereview.chromium.org/316253003/diff/20001/runtime/vm/scanner.cc
File runtime/vm/scanner.cc (right):

https://codereview.chromium.org/316253003/diff/20001/runtime/vm/scanner.cc#ne...
runtime/vm/scanner.cc:42: private:
IMO it does not really make much sense to make this private and then have to
declare Scanner and ScanContext as fiends.  Why not simply leave everything
public and forget the accessors?

[srdjan, 2014-06-05 22:03:51]

https://codereview.chromium.org/316253003/diff/20001/runtime/vm/scanner.cc
File runtime/vm/scanner.cc (right):

https://codereview.chromium.org/316253003/diff/20001/runtime/vm/scanner.cc#ne...
runtime/vm/scanner.cc:42: private:
On 2014/06/05 21:58:54, hausner wrote:
> IMO it does not really make much sense to make this private and then have to
> declare Scanner and ScanContext as fiends.  Why not simply leave everything
> public and forget the accessors?
>  

Discussed offline, leaving it as it is.

[srdjan, 2014-06-05 22:04:21]

Committed patchset #2 manually as r37053 (presubmit successful).