dart2js: permit generation of conditionals as arguments of allocations.

dart2js: permit generation of conditionals as arguments of allocations.

Example:

    t1 = onError == null ? 1 : 3;
    this._addListener$1(new P._FutureListener(null, result, t1, f, onError));
-->
    this._addListener$1(new P._FutureListener(null, result, onError == null ? 1 : 3, f, onError));

R=herhut@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44696

[sra1, 2015-03-24 23:47:31]

sra@google.com changed reviewers:
+ herhut@google.com

[herhut, 2015-03-25 10:02:45]

lgtm

[sra1, 2015-03-25 20:18:42]

Committed patchset #1 (id:1) manually as 44696 (presubmit successful).