aura: Remove CreateOffscreenContext from ui::ContextFactory.

content/browser/aura/gpu_process_transport_factory.cc

Index: content/browser/aura/gpu_process_transport_factory.cc
diff --git a/content/browser/aura/gpu_process_transport_factory.cc b/content/browser/aura/gpu_process_transport_factory.cc
index 47b1533ae77617772a67355c9e988f37d19114d0..eeb6f3bc5786e443ad978d6774313073365d37de 100644
--- a/content/browser/aura/gpu_process_transport_factory.cc
+++ b/content/browser/aura/gpu_process_transport_factory.cc
@@ -199,12 +199,6 @@ GpuProcessTransportFactory::CreateOffscreenCommandBufferContext() {
   return CreateContextCommon(swap_client, 0);
 }
 
-scoped_ptr<WebKit::WebGraphicsContext3D>
-GpuProcessTransportFactory::CreateOffscreenContext() {
-  return CreateOffscreenCommandBufferContext()
-      .PassAs<WebKit::WebGraphicsContext3D>();
-}
-
 scoped_ptr<cc::SoftwareOutputDevice> CreateSoftwareOutputDevice(
     ui::Compositor* compositor) {
 #if defined(OS_WIN)