Update assertion in LayoutBox::intrinsicScrollbarLogicalWidth.

Tolerate nonexistent scrollbar in LayoutBox::intrinsicScrollbarLogicalWidth.

DeprecatedPaintLayerScrollableArea will not create an overlay scrollbar if there
is no overflow on that axis, even if overflow:scroll is specified.  This is
intentional behavior added in http://crbug.com/415031.

It's correct for intrinsicScrollbarLogicalWidth to return 0 in this case, as it
already does for all overlay scrollbars.

BUG=520662
TEST=WebViewTest.GeolocationAPIEmbedderHasAccessAllow passes on Mac

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200911

[skobes, 2015-08-20 01:43:23]

skobes@chromium.org changed reviewers:
+ eae@chromium.org

[skobes, 2015-08-20 01:43:52]

The CQ bit was checked by skobes@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-20 01:43:57]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1292003007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1292003007/1

[commit-bot: I haz the power, 2015-08-20 02:11:33]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-20 02:11:33]

Dry run: Try jobs failed on following builders:
  chromeos_daisy_chromium_compile_only_ng on tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_daisy_...)

[skobes, 2015-08-20 02:32:44]

The CQ bit was checked by skobes@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-20 02:32:52]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1292003007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1292003007/1

[commit-bot: I haz the power, 2015-08-20 03:08:10]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-20 03:08:10]

Dry run: Try jobs failed on following builders:
  chromeos_amd64-generic_chromium_compile_only_ng on tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_amd64-...)

[eae, 2015-08-20 17:05:06]

LGTM

[eae, 2015-08-20 17:05:10]

The CQ bit was checked by eae@chromium.org

[commit-bot: I haz the power, 2015-08-20 17:05:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1292003007/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1292003007/1

[commit-bot: I haz the power, 2015-08-20 17:32:15]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200911