Make GraphicsContext3DPrivate of GTK port shareable.

Make GraphicsContext3DPrivate of GTK port shareable.
https://bugs.webkit.org/show_bug.cgi?id=77296

Patch by ChangSeok Oh <shivamidow@gmail.com> on 2012-01-30
Reviewed by Eric Seidel.

GraphicsContext3DPrivate.cpp/h of GTK port look shareable with another port
using glx backend for WebGL. For example, EFL port.
Moved GraphicsContext3DPrivate.cpp and its header into Source/WebCore/platform/graphics/glx.

No new tests required, because of no new feature.

* GNUmakefile.am:
* GNUmakefile.list.am:
* platform/graphics/glx/GraphicsContext3DPrivate.cpp: Renamed from Source/WebCore/platform/graphics/gtk/GraphicsContext3DPrivate.cpp.
(sharedDisplay):
(WebCore):
(WebCore::activeGraphicsContexts):
(WebCore::GraphicsContext3DPrivate::addActiveGraphicsContext):
(WebCore::GraphicsContext3DPrivate::removeActiveGraphicsContext):
(WebCore::GraphicsContext3DPrivate::cleanupActiveContextsAtExit):
(WebCore::GraphicsContext3DPrivate::create):
(WebCore::GraphicsContext3DPrivate::createPbufferContext):
(WebCore::GraphicsContext3DPrivate::createPixmapContext):
(WebCore::GraphicsContext3DPrivate::GraphicsContext3DPrivate):
(WebCore::GraphicsContext3DPrivate::~GraphicsContext3DPrivate):
(WebCore::GraphicsContext3DPrivate::makeContextCurrent):
* platform/graphics/glx/GraphicsContext3DPrivate.h: Renamed from Source/WebCore/platform/graphics/gtk/GraphicsContext3DPrivate.h.
(WebCore):
(GraphicsContext3DPrivate):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106220 268f45cc-cd09-0410-ab3c-d52691b4dbfc