Fix city-list example after changes to scrolling

Fix city-list example after changes to scrolling.

Note that this patch only includes support for the wheel event.
I'll follow-up with a patch for scrolling/fling when I have a setup
on which I can verify that working.

R=esprehn@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/44d2c0a13d2350e866945ae2c624c3e06539f5a3

[rafaelw, 2015-01-29 00:30:00]

rafaelw@chromium.org changed reviewers:
+ abarth@chromium.org

[esprehn, 2015-01-29 00:33:53]

esprehn@chromium.org changed reviewers:
+ esprehn@chromium.org

[esprehn, 2015-01-29 00:33:54]

lgtm, but you can remove the transformY(0) too.

https://codereview.chromium.org/875473004/diff/1/sky/examples/city-list/city-...
File sky/examples/city-list/city-list.sky (right):

https://codereview.chromium.org/875473004/diff/1/sky/examples/city-list/city-...
sky/examples/city-list/city-list.sky:124: transform: translateY(0);
You don't need this anymore. A 0 transform has no effect since we don't do layer
promotion or compositing.

[esprehn, 2015-01-29 00:34:07]

On 2015/01/29 at 00:33:54, esprehn wrote:
> lgtm, but you can remove the transformY(0) too.
> 
>
https://codereview.chromium.org/875473004/diff/1/sky/examples/city-list/city-...
> File sky/examples/city-list/city-list.sky (right):
> 
>
https://codereview.chromium.org/875473004/diff/1/sky/examples/city-list/city-...
> sky/examples/city-list/city-list.sky:124: transform: translateY(0);
> You don't need this anymore. A 0 transform has no effect since we don't do
layer promotion or compositing.

Or maybe you wanted will-change: transform to become a stacking context?

[abarth-chromium, 2015-01-29 00:35:28]

On 2015/01/29 at 00:34:07, esprehn wrote:
> Or maybe you wanted will-change: transform to become a stacking context?

Yeah, will-change: transform is a better way of doing this.

[abarth-chromium, 2015-01-29 00:36:08]

I wish there was some way to share code between sky-scrollable and city-list. 
Maybe there's some base class to extract that has all the event listeners and
the fling curve?

[rafaelw, 2015-01-29 00:40:26]

updated to use will-change: transform

[rafaelw, 2015-01-29 00:56:39]

Committed patchset #3 (id:40001) manually as
44d2c0a13d2350e866945ae2c624c3e06539f5a3 (presubmit successful).