[BlackBerry] GraphicsContext3D: don't initialize m_extensions in the constructor
https://bugs.webkit.org/show_bug.cgi?id=114726

Patch by Alberto Garcia <agarcia@igalia.com> on 2013-04-17
Reviewed by Carlos Garcia Campos.

m_extensions is now initialized on demand by
GraphicsContext3D::getExtensions().

Doing it in the constructor produces a crash, because
Extensions3DOpenGLES() calls glGetString before the WebGL context
is current.

* platform/graphics/blackberry/GraphicsContext3DBlackBerry.cpp:
(WebCore::GraphicsContext3D::GraphicsContext3D):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148595 268f45cc-cd09-0410-ab3c-d52691b4dbfc