Remove unused members from LayerChromium.

Remove unused members from LayerChromium.
These members are never set, and never used.
Other members that are set but not used have been left (we may use them
later, e.g. m_opaque).
https://bugs.webkit.org/show_bug.cgi?id=68297

Patch by Antoine Labour <piman@chromium.org> on 2011-09-22
Reviewed by James Robinson.

No functional change, no new test needed.

* platform/graphics/chromium/LayerChromium.cpp:
(WebCore::LayerChromium::LayerChromium):
* platform/graphics/chromium/LayerChromium.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@95776 268f45cc-cd09-0410-ab3c-d52691b4dbfc