Reviewed by Geoffrey Garen.

Source/WebCore: 

Allow WebKitSystemInterface to draw scrollbars 
when appropriate.
* WebCore.exp.in:
* platform/mac/ScrollbarThemeMac.mm:
(WebCore::scrollbarMap):
(+[ScrollbarPrefsObserver appearancePrefsChanged:]):
(WebCore::ScrollbarThemeMac::registerScrollbar):
(WebCore::ScrollbarThemeMac::unregisterScrollbar):
(WebCore::ScrollbarThemeMac::paint):
* platform/mac/WebCoreSystemInterface.h:
* platform/mac/WebCoreSystemInterface.mm:

Source/WebKit/mac: 

Allow WebKitSystemInterface to draw scrollbars 
when appropriate.
* WebCoreSupport/WebSystemInterface.mm:
(InitWebCoreSystemInterface):

Source/WebKit2: 

Allow WebKitSystemInterface to draw scrollbars 
when appropriate.
* WebProcess/WebCoreSupport/mac/WebSystemInterface.mm:
(InitWebCoreSystemInterface):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@76292 268f45cc-cd09-0410-ab3c-d52691b4dbfc