ToT.

We noticed that the new launcher animation is jank on ELM.

We have several things need to do:

1. newcomer@ will investigate the jank and resolve it.
2. backup plan is that, in the mean while weidongg@ will add a flag at chrome side to disable animation with this flag.
3. with 2, wutao@ will add a device specific flag at chromeOS side to append the chrome flag, so that there is no new launcher animation on ELM.