Show a vertical scrollbar (when needed) for overflow:-webkit-paged-y.

Show a vertical scrollbar (when needed) for overflow:-webkit-paged-y.

We were already showing a horizontal scrollbar for -webkit-paged-x. For
-webkit-paged-y, on the other hand, it only worked when it was the viewport
that was paginated, but not when specified on a regular block.

The CSS parser currently deals with the overflow shorthand in such a way that
it's the overflow-y property that gets the -webkit-paged-foo value (while
overflow-x becomes auto). Digression: While one could say that's not quite
right when it comes to horizontal writing modes, handling shorthands based on
writing mode would be nasty...

Skipping 2 of the new tests for the old / current multicol implementation,
since they fail there. All tests pass in the new implementation.

BUG=460024
R=dsinclair@chromium.org,jchaffraix@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190656

[rune, 2015-02-23 13:29:21]

rune@opera.com changed reviewers:
+ rune@opera.com

[rune, 2015-02-23 13:29:22]

lgtm

The description should say why you skip the tests in TestExpectations.

[mstensho (USE GERRIT), 2015-02-23 13:31:21]

On 2015/02/23 13:29:22, rune wrote:
> lgtm
> 
> The description should say why you skip the tests in TestExpectations.

Done.

[mstensho (USE GERRIT), 2015-02-23 13:31:25]

The CQ bit was checked by mstensho@opera.com

[commit-bot: I haz the power, 2015-02-23 13:32:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/940913002/1

[commit-bot: I haz the power, 2015-02-23 13:35:15]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190656