Handle null argument for Selection.selectAllChildren()

Handle null argument for Selection.selectAllChildren()

Blink r186929 "Make some Selection function arguments non-optional"
mistakenly assumed that this cannot be null, but without strict type
checking it can be.

Per spec anything other than Node should throw a TypeError, but begin
by reverting to the old state. Add a test that would trigger this
assert for which the pass condition can be inverted later.

BUG=443721
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187530

[philipj_slow, 2014-12-19 12:38:49]

philipj@opera.com changed reviewers:
+ fs@opera.com

[fs, 2014-12-19 12:47:50]

lgtm

[philipj_slow, 2014-12-19 13:03:36]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2014-12-19 13:04:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/817693002/1

[commit-bot: I haz the power, 2014-12-19 13:39:47]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=187530