dart2js cps: Support async/await by rewriting the JavaScript AST.

dart2js cps: Support async/await by rewriting the JavaScript AST.

BUG=
R=kmillikin@google.com

Committed: https://github.com/dart-lang/sdk/commit/bafb8fb191bfd07346523fb8f88c8b71ca630364

[karlklose, 2015-08-07 07:40:03]

Patchset #1 (id:1) has been deleted

[karlklose, 2015-08-07 07:40:10]

Patchset #1 (id:20001) has been deleted

[karlklose, 2015-08-07 07:41:09]

karlklose@google.com changed reviewers:
+ kmillikin@google.com

[Kevin Millikin (Google), 2015-08-07 08:52:33]

LGTM.

https://codereview.chromium.org/1253333002/diff/80001/pkg/compiler/lib/src/js...
File pkg/compiler/lib/src/js_backend/backend.dart (right):

https://codereview.chromium.org/1253333002/diff/80001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_backend/backend.dart:2764: else if (element.asyncMarker
== AsyncMarker.ASYNC_STAR) {
else if is on the wrong line.  I'd probably write a switch here and return from
each of the cases, but yours is OK too.

https://codereview.chromium.org/1253333002/diff/80001/pkg/compiler/lib/src/js...
pkg/compiler/lib/src/js_backend/backend.dart:2781: return rewriter != null ?
rewriter.rewrite(code) : code;
It seems like the only call is guarded by asyncMarker != AsyncMarker.SYNC.  I
think it's clearer to either assert that (and so rewriter is not null unless we
get a new AsyncMarker), or else to call this function unconditionally because it
can handle any function.

[karlklose, 2015-08-07 09:27:45]

Committed patchset #4 (id:100001) manually as
bafb8fb191bfd07346523fb8f88c8b71ca630364 (presubmit successful).