Reuse function objects of async closure body

Reuse function objects of async closure body

When an async function is compiled, it creates a closure that contains the code of the async function’s body. Before this change, a new function object is created each time the async function is compiled. This change looks up previously created closures and reuses them, similar to what the parser does for local functions.

R=rmacnak@google.com

Committed: https://code.google.com/p/dart/source/detail?r=41084

[hausner, 2014-10-13 20:42:51]

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

[rmacnak, 2014-10-13 21:33:15]

LGTM

[hausner, 2014-10-13 21:38:17]

Committed patchset #2 (id:60001) manually as r41084 (presubmit successful).