[BlackBerry] fix confusing destruction sequence in LayerCompositingThread

[BlackBerry] fix confusing destruction sequence in LayerCompositingThread
https://bugs.webkit.org/show_bug.cgi?id=81706

Patch by Joe Mason <jmason@rim.com> on 2012-03-27
Reviewed by Rob Buis.

LayerCompositingThread has a destructor that does a synchronous
dispatch to the compositing thread and then does the actual cleanup
from a helper function. This is confusing.It should be the
opposite: the helper function dispatches to the compositing thread,
which calls delete.

No new tests since the existing animation tests will exercise this
code.

* platform/graphics/blackberry/LayerCompositingThread.cpp:
(WebCore::LayerCompositingThread::destroyOnCompositingThread):
(WebCore):
(WebCore::LayerCompositingThread::~LayerCompositingThread):
* platform/graphics/blackberry/LayerCompositingThread.h:
(LayerCompositingThread):
(WTF):
(WTF::::deref):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@112304 268f45cc-cd09-0410-ab3c-d52691b4dbfc