Remove dead RenderLayerCompositor::setCompositingParent

Remove dead RenderLayerCompositor::setCompositingParent

This code is dead, we always pass a null parentLayer which causes us to
early return. I think we were supposed to call
childLayer->compositedLayerMapping()->childForSuperlayers()->removeFromParent()
in the original design, but since r44876 [1] we always early return when the
parentLayer is null, and that patch was back in 2009 so clearly the code
is not needed.

[1] http://src.chromium.org/viewvc/blink?revision=44876&view=revision

R=abarth@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173705

[chrishtr, 2014-05-09 01:08:44]

lgtm

[commit-bot: I haz the power, 2014-05-09 01:09:56]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/esprehn@chromium.org/279643002/1

[commit-bot: I haz the power, 2014-05-09 02:19:59]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  linux_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/6763)
  mac_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/6268)

[commit-bot: I haz the power, 2014-05-09 02:59:06]

Change committed as 173705

[abarth-chromium, 2014-05-09 03:02:36]

https://codereview.chromium.org/279643002/diff/1/Source/core/rendering/compos...
File Source/core/rendering/compositing/RenderLayerCompositor.cpp (left):

https://codereview.chromium.org/279643002/diff/1/Source/core/rendering/compos...
Source/core/rendering/compositing/RenderLayerCompositor.cpp:684: GraphicsLayer*
hostedLayer = childLayer->compositedLayerMapping()->childForSuperlayers();
Do parentForSublayers and childForSuperlayers still have clients?