Stub in Mac viewer code.

tools/viewer/sk_app/mac/GLWindowContext_mac.h

Index: tools/viewer/sk_app/mac/GLWindowContext_mac.h
diff --git a/tools/viewer/sk_app/unix/GLWindowContext_unix.h b/tools/viewer/sk_app/mac/GLWindowContext_mac.h
similarity index 65%
copy from tools/viewer/sk_app/unix/GLWindowContext_unix.h
copy to tools/viewer/sk_app/mac/GLWindowContext_mac.h
index 2d76254c21012d710557dae0c2f00aff56452305..e889c4cd310194c1f2a37719194341342fe9180e 100644
--- a/tools/viewer/sk_app/unix/GLWindowContext_unix.h
+++ b/tools/viewer/sk_app/mac/GLWindowContext_mac.h
@@ -5,19 +5,19 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
-#ifndef GLWindowContext_unix_DEFINED
-#define GLWindowContext_unix_DEFINED
+#ifndef GLWindowContext_mac_DEFINED
+#define GLWindowContext_mac_DEFINED
 
 #include "../GLWindowContext.h"
-#include "Window_unix.h"
+#include "Window_mac.h"
 
 namespace sk_app {
 
-class GLWindowContext_unix : public GLWindowContext {
+class GLWindowContext_mac : public GLWindowContext {
 public:
     friend GLWindowContext* GLWindowContext::Create(void* platformData, const DisplayParams&);
 
-    ~GLWindowContext_unix() override;
+    ~GLWindowContext_mac() override;
 
     void onSwapBuffers() override;
 
@@ -25,12 +25,15 @@ public:
     void onDestroyContext() override;
 
 private:
-    GLWindowContext_unix(void*, const DisplayParams&);
+    GLWindowContext_mac(void*, const DisplayParams&);
 
+#if 0
+    // TODO: add Mac-specific GL display objects
     Display*     fDisplay;
     XWindow      fWindow;
     XVisualInfo* fVisualInfo;
     GLXContext   fGLContext;
+#endif
 };