Allow the render context to do necessary work when the video mode changes.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%402017

src/video/cocoa/SDL_cocoaopengl.m

@@ -268,6 +268,7 @@ Cocoa_GL_MakeCurrent(_THIS, SDL_Window * window, SDL_GLContext context)
         NSOpenGLContext *nscontext = (NSOpenGLContext *)context;
 
         [nscontext setView:[windowdata->window contentView]];
+        [nscontext update];
         [nscontext makeCurrentContext];
     } else {
         [NSOpenGLContext clearCurrentContext];