Add a basic NativeViewportMac for Mojo

ui/gl/gl_context_nsview.h

 // 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.
 
 #ifndef UI_GL_GL_CONTEXT_NSVIEW_H_
 #define UI_GL_GL_CONTEXT_NSVIEW_H_
 
 #import <AppKit/NSOpenGL.h>
 
 #include "base/compiler_specific.h"
 #include "base/mac/scoped_nsobject.h"
 #include "ui/gl/gl_context.h"
 
 namespace gfx {
 
 class GLSurface;
 
 // GLContextNSView encapsulates an NSView-based GLContext.  This is paired with
 // the GLSurfaceNSView class.
 class GLContextNSView : public GLContextReal {
  public:
   explicit GLContextNSView(GLShareGroup* group);
-  virtual ~GLContextNSView();
 
   // GLContext:
   virtual bool Initialize(GLSurface* surface,
                           GpuPreference gpu_preference) OVERRIDE;
   virtual void Destroy() OVERRIDE;
   virtual bool MakeCurrent(GLSurface* surface) OVERRIDE;
   virtual void ReleaseCurrent(GLSurface* surface) OVERRIDE;
   virtual bool IsCurrent(GLSurface* surface) OVERRIDE;
   virtual void* GetHandle() OVERRIDE;
   virtual void SetSwapInterval(int interval) OVERRIDE;
 
   // Flush the |context_|.  Swaps buffers.
   void FlushBuffer();
 
  private:
+  virtual ~GLContextNSView();
+
   base::scoped_nsobject<NSOpenGLContext> context_;
   GpuPreference gpu_preference_;
 
   DISALLOW_COPY_AND_ASSIGN(GLContextNSView);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_CONTEXT_NSVIEW_H_