Fix scoping async functions.

Fix scoping async functions.

This CL fixes several scoping/context issues:
* Do not reuse scopes in SequenceNode_s as they might introduce a new context
  level. In that case we would trigger context allocationg multiple times
  resulting in scope/contexts being out of sync.
* Properly save and restore saved_try_context in try/catch/finally blocks and
  nesting closures. For this we need to keep track of async closures top scopes.

R=hausner@google.com

Committed: https://code.google.com/p/dart/source/detail?r=39775

[Michael Lippautz (Google), 2014-09-02 18:11:24]

Patchset #4 (id:60001) has been deleted

[Michael Lippautz (Google), 2014-09-02 18:11:30]

Patchset #3 (id:40001) has been deleted

[Michael Lippautz (Google), 2014-09-02 18:11:39]

Patchset #1 (id:1) has been deleted

[Michael Lippautz (Google), 2014-09-02 18:11:44]

Patchset #1 (id:20001) has been deleted

[Michael Lippautz (Google), 2014-09-02 18:22:10]

mlippautz@google.com changed reviewers:
+ hausner@google.com

[Michael Lippautz (Google), 2014-09-02 18:22:11]

PTAL

There's no more dry run, as we now properly add variables to scopes in the first
run. (And we do the same in subsequent runs.)

https://codereview.chromium.org/520223002/diff/80001/runtime/vm/parser.h
File runtime/vm/parser.h (right):

https://codereview.chromium.org/520223002/diff/80001/runtime/vm/parser.h#newc...
runtime/vm/parser.h:188: String& async_saved_try_ctx_name_;
It's not ideal that we need to save the symbol in the one case and the variable
in the other... 

We need to look up the async version though as the try/catch/finally might live
in a context level further down.

[hausner, 2014-09-02 20:04:47]

lgtm

https://codereview.chromium.org/520223002/diff/80001/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/520223002/diff/80001/runtime/vm/parser.cc#new...
runtime/vm/parser.cc:2947: LocalVariable* saved_saved_try_ctx =
parsed_function()->saved_try_ctx();
We only have to save and restore these values if a nested function is parsed,
right?

[Michael Lippautz (Google), 2014-09-02 20:25:23]

https://codereview.chromium.org/520223002/diff/80001/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/520223002/diff/80001/runtime/vm/parser.cc#new...
runtime/vm/parser.cc:2947: LocalVariable* saved_saved_try_ctx =
parsed_function()->saved_try_ctx();
On 2014/09/02 20:04:47, hausner wrote:
> We only have to save and restore these values if a nested function is parsed,
> right?

Yes, I added a comment.

[Michael Lippautz (Google), 2014-09-02 20:25:44]

Committed patchset #2 (id:100001) manually as 39775 (presubmit successful).