Pass rootNode by reference when constructing node lists / collections

Pass rootNode by reference when constructing node lists / collections

Pass rootNode by reference when constructing node lists / collections to make
it clear that the rootNode cannot be null. Their implementation already relies
on the fact that the rootNode cannot be null.

R=adamk@chromium.org, adamk

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=168417

[adamk, 2014-03-04 19:51:55]

rslgtm

[adamk, 2014-03-04 19:51:59]

The CQ bit was checked by adamk@chromium.org

[commit-bot: I haz the power, 2014-03-04 19:53:12]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/176933013/1

[Inactive, 2014-03-05 02:26:20]

Committed patchset #2 manually as r168417 (presubmit successful).