Add a new ozone switch to enable surfaceless output mode.

ui/ozone/public/surface_factory_ozone.h

Index: ui/ozone/public/surface_factory_ozone.h
diff --git a/ui/ozone/public/surface_factory_ozone.h b/ui/ozone/public/surface_factory_ozone.h
index 08b977459b202f92cf470fe491f46ca144e72bbf..4f312cac49a6ae8e0fbb3fef9bb69eb50b38e0bc 100644
--- a/ui/ozone/public/surface_factory_ozone.h
+++ b/ui/ozone/public/surface_factory_ozone.h
@@ -90,6 +90,12 @@ class OZONE_BASE_EXPORT SurfaceFactoryOzone {
   virtual scoped_ptr<SurfaceOzoneEGL> CreateEGLSurfaceForWidget(
       gfx::AcceleratedWidget widget);
 
+  // Create an EGL surface that isn't backed by any buffers, and is used
+  // for overlay-only displays. This will return NULL if this mode is
+  // not supported.
+  virtual scoped_ptr<SurfaceOzoneEGL> CreateSurfacelessEGLSurfaceForWidget(
+      gfx::AcceleratedWidget widget);
+
   // Create SurfaceOzoneCanvas for the specified gfx::AcceleratedWidget.
   //
   // Note: The platform must support creation of SurfaceOzoneCanvas from the