Fix scrollbar thumb drag cancellation in RTL mode

Fix scrollbar thumb drag cancellation in RTL mode

Scrollbar stores original scroll position in non-negative scroll coordinates.
When sending those coordinates to ScrollableArea, they should be offsetted
with minimumScrollPosition() first.

R=jchaffraix@chromium.org
BUG=377131
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175100

[trchen, 2014-05-28 00:34:33]

This is a simple one-line fix. PTAL, thanks!

[trchen, 2014-05-28 23:30:55]

Ping?

[Julien - ping for review, 2014-05-29 18:15:49]

lgtm

https://codereview.chromium.org/302603009/diff/20001/LayoutTests/platform/mac...
File
LayoutTests/platform/mac/fast/overflow/rtl-scrollbar-drag-origin-expected.txt
(right):

https://codereview.chromium.org/302603009/diff/20001/LayoutTests/platform/mac...
LayoutTests/platform/mac/fast/overflow/rtl-scrollbar-drag-origin-expected.txt:2:
FAIL container.scrollLeft should be 350. Was 0.
I assume this fails due to overlay scrollbars on Mac. I wonder if mock
scrollbars would help (I don't think so but worth a try) or at least we should
have a comment in the output that we expect this to fail on Mac due these
scrollbars.

[trchen, 2014-05-29 20:53:26]

On 2014/05/29 18:15:49, Julien Chaffraix - PST wrote:
> lgtm
> 
>
https://codereview.chromium.org/302603009/diff/20001/LayoutTests/platform/mac...
> File
> LayoutTests/platform/mac/fast/overflow/rtl-scrollbar-drag-origin-expected.txt
> (right):
> 
>
https://codereview.chromium.org/302603009/diff/20001/LayoutTests/platform/mac...
>
LayoutTests/platform/mac/fast/overflow/rtl-scrollbar-drag-origin-expected.txt:2:
> FAIL container.scrollLeft should be 350. Was 0.
> I assume this fails due to overlay scrollbars on Mac. I wonder if mock
> scrollbars would help (I don't think so but worth a try) or at least we should
> have a comment in the output that we expect this to fail on Mac due these
> scrollbars.

Mac doesn't have the behavior that scrolling cancels when mouse cursor if out of
a certain range. I'll add that comment in the test.

[trchen, 2014-05-29 21:10:05]

The CQ bit was checked by trchen@chromium.org

[commit-bot: I haz the power, 2014-05-29 21:10:50]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/trchen@chromium.org/302603009/30001

[commit-bot: I haz the power, 2014-05-30 03:25:49]

Change committed as 175100