Reuse the top ApiLocalScope so that we do not allocate and free an ApiLocalScope

Reuse the top ApiLocalScope so that we do not allocate and free an ApiLocalScope
for each Dart_EnterScope/Dart_ExitScope sequence.

The runtime of UseDartApi benchmark on linux ia32 improves from
187316 to 121083.

R=srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=25292

[srdjan, 2013-07-22 18:18:16]

lgtm

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_impl.c...
runtime/vm/dart_api_impl.cc:1101: delete scope;
assert reusable_scope != scope

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_state.h
File runtime/vm/dart_api_state.h (right):

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_state....
runtime/vm/dart_api_state.h:105: if (isolate != NULL && isolate->current_zone()
== &zone_) {
Say: parentheseeeeeeees

[siva, 2013-07-22 18:42:08]

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_impl.cc
File runtime/vm/dart_api_impl.cc (right):

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_impl.c...
runtime/vm/dart_api_impl.cc:1101: delete scope;
On 2013/07/22 18:18:16, srdjan wrote:
> assert reusable_scope != scope

Done.

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_state.h
File runtime/vm/dart_api_state.h (right):

https://codereview.chromium.org/19974002/diff/7001/runtime/vm/dart_api_state....
runtime/vm/dart_api_state.h:105: if (isolate != NULL && isolate->current_zone()
== &zone_) {
Done :-)

On 2013/07/22 18:18:16, srdjan wrote:
> Say: parentheseeeeeeees

[siva, 2013-07-22 18:46:19]

Committed patchset #3 manually as r25292 (presubmit successful).