Wire up SDL on mac

src/views/sdl/SkOSWindow_SDL.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkOSWindow_SDL.h"
 #include "SkCanvas.h"
 
 #if defined(SK_BUILD_FOR_ANDROID)
 #include <GLES/gl.h>
-#else
+#elif defined(SK_BUILD_FOR_LINUX)
 #include <GL/gl.h>
+#elif defined(SK_BUILD_FOR_MAC)
+#include <gl.h>
 #endif
 
 const int SCREEN_WIDTH = 640;
 const int SCREEN_HEIGHT = 480;
 
 static void handle_error() {
     const char* error = SDL_GetError();
     SkDebugf("SDL Error: %s\n", error);
     SDL_ClearError();
 }
@@ skipping 256 matching lines @@
 
     // Start normal Skia sequence
     application_init();
 
     window->loop();
 
     delete window;
     application_term();
     return 0;
 }