ozone: Clarify All SurfaceFactoryOzone APIs except for CreateNativePixmap() must be used on the mai…

ui/ozone/platform/drm/drm_surface_factory.cc

Index: ui/ozone/platform/drm/drm_surface_factory.cc
diff --git a/ui/ozone/platform/drm/drm_surface_factory.cc b/ui/ozone/platform/drm/drm_surface_factory.cc
index 6fbf2606dc7a059ddbcea678aa2c0c9de0131078..ccbbf2bb0f25e8b739df8252e2afa67bffc59e33 100644
--- a/ui/ozone/platform/drm/drm_surface_factory.cc
+++ b/ui/ozone/platform/drm/drm_surface_factory.cc
@@ -25,12 +25,14 @@ DrmSurfaceFactory::~DrmSurfaceFactory() {
 
 scoped_ptr<ui::SurfaceOzoneCanvas> DrmSurfaceFactory::CreateCanvasForWidget(
     gfx::AcceleratedWidget widget) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   return make_scoped_ptr(new DrmSurface(screen_manager_->GetWindow(widget)));
 }
 
 bool DrmSurfaceFactory::LoadEGLGLES2Bindings(
     AddGLLibraryCallback add_gl_library,
     SetGLGetProcAddressProcCallback set_gl_get_proc_address) {
+  DCHECK(thread_checker_.CalledOnValidThread());
   return false;
 }