Revert of Revert of Don't check for layout in a canvas if it it's already needed

Revert of Revert of Don't check for layout in a canvas if it it's already needed (patchset #1 id:1 of https://codereview.chromium.org/810943003/)

Reason for revert:
Speculative revert did not fix crbug.com/446834

Original issue's description:
> Revert of Don't check for layout in a canvas if it it's already needed (patchset #3 id:40001 of https://codereview.chromium.org/828163002/)
> 
> Reason for revert:
> Speculative revert for crashes on WinXP bots. See crbug.com/446834
> I will re-land if this does not fix the crashes.
> 
> Original issue's description:
> > Don't check for layout in a canvas if it it's already needed
> > 
> > In this clusterfuzz test case a float is deleted but its entry in the floating
> > objects list of a sibling renderer is accessed before layout has had time to
> > remove reference to it. The read attempt pre-empts layout because the change in
> > zoom factor prompts the canvas renderer to recompute its width/height to check
> > if layout is required. If layout is already required this isn't necessary and,
> > what's more, if layout is already required it may be because renderer(s) in its
> > floating object list have been deleted and aren't safe to access while computing
> > offset as part of the width calculations.
> > 
> > So return early when the check for layout is unnecessary and may even crash.
> > 
> > BUG=445285
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187935
> 
> TBR=dsinclair@chromium.org,inferno@chromium.org,jchaffraix@chromium.org,jshin@chromium.org,pdr@chromium.org,robhogan@gmail.com
> NOTREECHECKS=true
> NOTRY=true
> BUG=445285
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187981

TBR=dsinclair@chromium.org,inferno@chromium.org,jchaffraix@chromium.org,jshin@chromium.org,pdr@chromium.org,robhogan@gmail.com
NOTREECHECKS=true
NOTRY=true
BUG=445285
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=187985

[Justin Novosad, 2015-01-07 18:07:23]

Created Revert of Revert of Don't check for layout in a canvas if it it's
already needed

[commit-bot: I haz the power, 2015-01-07 18:07:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/837233002/1

[commit-bot: I haz the power, 2015-01-07 18:08:10]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=187985