Dispel the myth that enclosingLayer can return zero

Dispel the myth that enclosingLayer can return zero

A bunch of code was needlessly null-checking enclosingLayer. That function can
only return zero for RenderObjects that are outside of the render tree.

R=esprehn@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170233

[esprehn, 2014-03-27 23:51:19]

lgtm, but perhaps enclosingLayer() should return a reference and ASSERT() you're
in the tree?

[abarth-chromium, 2014-03-28 00:10:04]

On 2014/03/27 23:51:19, esprehn wrote:
> lgtm, but perhaps enclosingLayer() should return a reference and ASSERT()
you're
> in the tree?

There's one caller (in RenderObject::willChangeStyle) that calls it while you're
not in the tree.  The ASSERT is in https://codereview.chromium.org/215773002/

[abarth-chromium, 2014-03-28 00:10:10]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-03-28 00:11:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/215843002/1

[commit-bot: I haz the power, 2014-03-28 00:58:15]

Change committed as 170233