Disable PDFBrowserTest.Scroll on Chrome OS

Disable PDFBrowserTest.Scroll on Chrome OS

It fails on the official builders.

BUG=446221
TEST=none
TBR=thestig@chromium.org
NOTRY=true

Committed: https://crrev.com/337db9a37656c022d52aa47c661ab757dce32bc3
Cr-Commit-Position: refs/heads/master@{#313829}

[James Cook, 2015-01-29 23:45:42]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2015-01-29 23:45:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/885973002/1

[commit-bot: I haz the power, 2015-01-29 23:47:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-29 23:47:54]

Patchset 1 (id:??) landed as
https://crrev.com/337db9a37656c022d52aa47c661ab757dce32bc3
Cr-Commit-Position: refs/heads/master@{#313829}

[Lei Zhang, 2015-01-29 23:54:05]

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

[Lei Zhang, 2015-01-29 23:54:05]

Sure, I'll try to figure these out.

[Lei Zhang, 2015-01-29 23:54:13]

Err, lgtm

[James Cook, 2015-01-29 23:55:38]

On 2015/01/29 23:54:13, Lei Zhang wrote:
> Err, lgtm

piman was looking over my shoulder and thought there might be a race between the
compositor thread (handling the mouse wheel event? not sure) and JavaScript
execution to fetch the scroll position.