Fix shadow repaint issue in vertical-rl mode

Fix shadow repaint issue in vertical-rl mode

The original code erroneously flipped the shadow edges when the box is
in vertical-rl writing mode, causing incorrect visual overflow and
repaint rects.

Our actual painting code for shadow is correct. The bug is just about
incorrect invalidation rects.

Note because of other bugs about shadow invalidation, the expected
result of the new tests are not correct yet. Will rebaseline them
when the bugs are fixed in later changes.

References:
[1] http://dev.w3.org/csswg/css-writing-modes-3/#physical-only

BUG=388343
TEST=fast/box-shadow/shadow-box-resize-writing-mode.html
TEST=fast/box-shadow/shadow-box-resize.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177246

[Xianzhu, 2014-06-24 18:42:48]

Changed bug from crbug.com/380472 to more specific crbug.com/388343.

[Xianzhu, 2014-06-26 17:03:48]

ping...

[Xianzhu, 2014-06-26 22:01:18]

I've made the CL much smaller, leaving refactoring in later changes.

PTAL.

[leviw_travelin_and_unemployed, 2014-06-30 19:01:20]

Okay. LGTM.

[leviw_travelin_and_unemployed, 2014-06-30 19:01:28]

The CQ bit was checked by leviw@chromium.org

[commit-bot: I haz the power, 2014-06-30 19:01:46]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/wangxianzhu@chromium.org/347393007/20001

[commit-bot: I haz the power, 2014-06-30 20:06:42]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/1...)
  mac_gpu_retina_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/mac_gpu_retina_tr...)

[commit-bot: I haz the power, 2014-06-30 23:20:32]

Change committed as 177246