Use InternalArray during ObservedArraySplice to avoid page script interfering with self-hosted code

Use InternalArray during ObservedArraySplice to avoid page script interfering with self-hosted code.

This also has the happy side-effect of speeding up observed array splices by about 20-30%, as it avoids copying the entire deleted_contents array.

R=verwaest
LOG=Y
BUG=NONE

[adamk, 2014-05-29 23:52:18]

Seems like this could have a test?

[Toon Verwaest, 2014-06-02 09:31:15]

https://codereview.chromium.org/303223004/diff/1/src/array.js
File src/array.js (right):

https://codereview.chromium.org/303223004/diff/1/src/array.js#newcode772
src/array.js:772: var deleted_elements = [];
Now that you are fixing this above, can you also fix this here?

[rafaelw, 2014-06-02 20:32:55]

https://codereview.chromium.org/303223004/diff/1/src/array.js
File src/array.js (right):

https://codereview.chromium.org/303223004/diff/1/src/array.js#newcode772
src/array.js:772: var deleted_elements = [];
So I tried doing this, but array-natives-elements.js started failing in the
assertion that the elements kind of the returned array is fast smi.
InternalArray seems to be setup such that it's default elements storage is fast
holey elements.

On 2014/06/02 09:31:15, Toon Verwaest wrote:
> Now that you are fixing this above, can you also fix this here?

[rafaelw, 2014-06-04 17:56:55]

ping Toon.

I know that Adam asked for a test. I kind of feel like it's a bit strange since
we don't have any other tests which attempt to assert that page script *can't*
interfere with self-hosted built-ins in this way, but I'm happy to add one if
you'd like to see it.

[Toon Verwaest, 2014-06-05 14:03:31]

I think the fix for both the main path and the Object.observe path should be
done at the same time.

Is there any other reason than splice correctness why you did this fix? I agree
it should be fixed, but we should keep both paths in sync. If you don't have a
fix for the main path (which I can easily understand), I'd prefer to not fix the
Object.observe path for now either. (I personally don't plan on fixing it any
time soon though.)