Add a config to use deferred image decoding on bots.

Add a config to use deferred image decoding on bots.

Depends on https://codereview.appspot.com/7810045/ and a change to
chrome so that our SKPs will have encoded images.

[borenet, 2013-03-20 11:58:29]

LGTM

[reed1, 2013-03-20 14:35:06]

hmmm, will this change affect our perf numbers, or only correctness tests?

[scroggo, 2013-03-20 14:53:19]

On 2013/03/20 14:35:06, reed1 wrote:
> hmmm, will this change affect our perf numbers, or only correctness tests?

This change will affect neither. This will add an extra config. Once we have
SKPs with encoded bitmaps, that extra config will be slower. This change doesn't
add deferred image decoding to render pictures, but I will add it.

The other change, https://codereview.appspot.com/7810045/, could potentially
affect both, since Chrome might draw a different SKP when deferred image
decoding is turned on.

[scroggo, 2013-03-20 14:59:37]

Adding a step to render_pictures requires a change in buildbot/, not trunk
(Eric, please correct me if I'm wrong.) That change is at
https://codereview.appspot.com/7758045/

[reed1, 2013-03-20 15:05:24]

lgtm

[scroggo, 2013-05-14 18:30:13]

I've finally worked out the kinks in getting us SKPs with encoded bitmaps, so
this will now work once it's checked in.

Before I do, I wanted to make sure it's okay to add one more thing to the bots.

[borenet, 2013-05-14 18:31:37]

Okay to add this one, but we should collectively determine which configs we can
drop.