Rename LayoutStateDisabler to ForceHorriblySlowRectMapping

Rename LayoutStateDisabler to ForceHorriblySlowRectMapping

LayoutState keeps track of a handful of fields, but the most
important part is providing a fast-mapping between renderers
and their repaint container. For parts where the logic doesn't
work, we disable LayoutState, which causes us to fall back on
walking up the tree and slowly calculating our rects.

Renaming LayoutStateDisabler, which sounds relatively innocuous
and which most people have no idea of the implications of to
ForceHorriblySlowRectMapping, with the hopes of striking fear
into any dev or reviewer who hopes to introduce one.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176052

[ojan, 2014-06-12 18:35:23]

lgtm <3

[commit-bot: I haz the power, 2014-06-12 18:35:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/leviw@chromium.org/333743002/1

[commit-bot: I haz the power, 2014-06-12 20:17:06]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_blink_dbg on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_dbg/builds/1...)
  mac_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/11259)
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/11800)

[commit-bot: I haz the power, 2014-06-12 21:34:35]

Change committed as 176052