Add constructors for JSArray

This change makes it easier to put type parameters on JavaScript Arrays.

There is one special factory constructor for putting the type on an existing Array, and some higher level factory constructors that implement the common List subtypes.

The effect of this is to move the type parameter assignment from every "new List" site to a handful of site within JSArray.  This shrinks some programs by half a percent, e,g, 3k of swarm.

JSArray.toList() and JSArray.sublist() now return JSArrays with the expected type parameters.

R=karlklose@google.com, ngeoffray@google.com

Committed: https://code.google.com/p/dart/source/detail?r=30374

[sra1, 2013-11-14 18:53:41]

Hi Karl,

Kasper is busy with the conference, can you take a look?
Thanks!

[sra1, 2013-11-15 23:27:34]

ping

[ngeoffray, 2013-11-18 07:08:18]

LGTM!

https://codereview.chromium.org/70703002/diff/110013/sdk/lib/_internal/lib/js...
File sdk/lib/_internal/lib/js_array.dart (right):

https://codereview.chromium.org/70703002/diff/110013/sdk/lib/_internal/lib/js...
sdk/lib/_internal/lib/js_array.dart:41: factory JSArray.growable(int length) {
Is anyone using this constructor?

https://codereview.chromium.org/70703002/diff/110013/sdk/lib/_internal/lib/js...
File sdk/lib/_internal/lib/js_names.dart (right):

https://codereview.chromium.org/70703002/diff/110013/sdk/lib/_internal/lib/js...
sdk/lib/_internal/lib/js_names.dart:12: JSArray;
One line.

[karlklose, 2013-11-18 07:31:19]

LGTM.

[sra1, 2013-11-18 21:06:59]

Committed patchset #3 manually as r30374 (presubmit successful).