Enable RegionBasedColumns runtime flag for stable.

Enable RegionBasedColumns runtime flag for stable.

This ships the new multicol implementation.

Removed the virtual/stable multicol testsuites, since the old multicol
implementation is no longer testable (and will be removed from the code
shortly).

BUG=334335, 408123
R=dsinclair@chromium.org,jchaffraix@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=195913

[dsinclair, 2015-05-26 15:11:03]

The CQ bit was checked by dsinclair@chromium.org

[dsinclair, 2015-05-26 15:11:04]

lgtm

[commit-bot: I haz the power, 2015-05-26 15:11:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1152423003/1

[commit-bot: I haz the power, 2015-05-26 15:19:00]

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

[commit-bot: I haz the power, 2015-05-26 15:19:02]

Try jobs failed on following builders:
  blink_presubmit on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/blink_presubmit/builds/3...)

[mstensho (USE GERRIT), 2015-05-26 16:16:56]

Need moar l-g-t-m (Source/platform/). jchaffraix?

[Julien - ping for review, 2015-05-26 17:34:36]

Based on http://www.chromium.org/developers/calendar, this gives us a month to
stabilize the feature before branch point.

lgtm <3

[Julien - ping for review, 2015-05-26 17:34:40]

The CQ bit was checked by jchaffraix@chromium.org

[commit-bot: I haz the power, 2015-05-26 17:34:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1152423003/1

[commit-bot: I haz the power, 2015-05-26 17:40:29]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=195913