Add a basic NativeViewportMac for Mojo

ui/gl/gl_context_nsview.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_context_nsview.h"
 
 #include <vector>
 
 #import <AppKit/NSOpenGL.h>
 #import <AppKit/NSView.h>
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "ui/gl/gl_surface_nsview.h"
 
 namespace gfx {
 
 GLContextNSView::GLContextNSView(GLShareGroup* group)
-    : GLContext(group) {
+    : GLContextReal(group) {
 }
 
 GLContextNSView::~GLContextNSView() {
 }
 
 bool GLContextNSView::Initialize(GLSurface* surface,
                                  GpuPreference gpu_preference) {
   DCHECK(!context_) << "NSGLContext was previously initialized.";
   gpu_preference_ = gpu_preference;
 
@@ skipping 27 matching lines @@
 bool GLContextNSView::MakeCurrent(GLSurface* surface) {
   TRACE_EVENT0("gpu", "GLContextNSView::MakeCurrent");
   AcceleratedWidget view =
       static_cast<AcceleratedWidget>(surface->GetHandle());
   // Only set the context's view if the view is parented.
   // I.e. it is a valid drawable.
   if ([view window])
     [context_ setView:view];
   [context_ makeCurrentContext];
 
+  SetRealGLApi();
   SetCurrent(surface);
 
   if (!surface->OnMakeCurrent(this)) {
     LOG(ERROR) << "Unable to make gl context current.";
     return false;
   }
 
   return true;
 }
 
@@ skipping 13 matching lines @@
   DCHECK(interval == 0 || interval == 1);
   GLint swap = interval;
   [context_ setValues:&swap forParameter:NSOpenGLCPSwapInterval];
 }
 
 void GLContextNSView::FlushBuffer() {
   [context_ flushBuffer];
 }
 
 }  // namespace gfx