Ensure reducing the length of an array doesn't make it go holey.

test/mjsunit/regress/regress-delete-empty-double.js

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-var o = JSON.parse('{"a":2600753951}');
-assertEquals(2600753951, o.a);
+a = [1.1,2.2,3.3];
+a.length = 0;
+delete a[0];

[danno, 2012/10/31 18:23:11]

 assertTrue(%HasFastDoubleElements(a));
 assertTrue(%HasFastHoleyElements(a));

[Toon Verwaest, 2012/10/31 18:27:28]

Are you sure this should be holey? In my current implementation they stay
non-holey given that nothing was actually deleted.

On 2012/10/31 18:23:11, danno wrote:

[danno, 2012/10/31 20:15:09]

You're right. How about a second case that verifies that deleting element 0 of a
1-element array does make it holey?

On 2012/10/31 18:27:28, Toon Verwaest wrote: