[New Multicolumn] Create a virtual testsuite for the region based multicol impl.

It is currently possible to switch between the old and the new multicol
implementation though Javascript. This means that individual tests may
"choose" in which implementation they should be evaluated. We wish to
remove the use of this Javascript toggle where it's not necessary
(ultimately everywhere), and use virtual test suites instead---even in the
transitional period where both implementations exist.

This patch is the first in a series which aims to fix this.

The virtual/regionbasedmulticol suite tests everything in fast/multicol,
except the tests which fail because the baseline is based on the old
implementation of multicol. The skipped tests should later be evaluated
individually, and baselined in the virtual/regionbasedmulticol suite, if
applicable.

I have verified that all the tests we skip in the virtual test suite use
the old multicol implementation.

Note: The tests fast/multicol/mixed-opacity-test.html and
multicol/mixed-opacity-fixed-test.html are "new" tests which fail due to a
known bug.

BUG=334335
R=rune@opera.com

Review URL: https://codereview.chromium.org/343963002

git-svn-id: svn://svn.chromium.org/blink/trunk@177488 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Simplify FullscreenElementStack::fullScreenChangeDelayTimerFired()

This function was needlessly complicated:

 1. A null pointer is never pushed to the queues outside of this
    function, so by adding a null check for the internal push, the
    initial null handling can be removed.

 2. !node->inDocument() implies !document()->contains(node.get()), so
    the latter can be dropped from the condition.

No observable change is expected from this simplication.

Review URL: https://codereview.chromium.org/365993002

git-svn-id: svn://svn.chromium.org/blink/trunk@177489 bbb929c8-8fbe-4397-9dbb-9b2b20218538