Add missing files for GL unix viewer.

tools/viewer/sk_app/unix/GLWindowContext_unix.h

 
 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
-#ifndef GLWindowContext_win_DEFINED
-#define GLWindowContext_win_DEFINED
+#ifndef GLWindowContext_unix_DEFINED
+#define GLWindowContext_unix_DEFINED
 
-#include <windows.h>
 #include "../GLWindowContext.h"
+#include "Window_unix.h"
 
 namespace sk_app {
 
-class GLWindowContext_win : public GLWindowContext {
+class GLWindowContext_unix : public GLWindowContext {
 public:
     friend GLWindowContext* GLWindowContext::Create(void* platformData, const DisplayParams&);
 
-    ~GLWindowContext_win() override;
+    ~GLWindowContext_unix() override;
 
     void onSwapBuffers() override;
 
     void onInitializeContext(void*, const DisplayParams&) override;
     void onDestroyContext() override;
 
 private:
-    GLWindowContext_win(void*, const DisplayParams&);
+    GLWindowContext_unix(void*, const DisplayParams&);
 
-    HWND              fHWND;
-    HGLRC             fHGLRC;
+    Display*     fDisplay;
+    XWindow      fWindow;
+    XVisualInfo* fVisualInfo;
+    GLXContext   fGLContext;
 };
 
 
 }
 
 #endif