Get Mac viewer working with SDL

Also fixes SkiaSDLExample.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2210603003

Review-Url: https://codereview.chromium.org/2210603003
diff --git a/example/SkiaSDLExample.cpp b/example/SkiaSDLExample.cpp
index da5f2dc..0072f0f 100644
--- a/example/SkiaSDLExample.cpp
+++ b/example/SkiaSDLExample.cpp
@@ -20,7 +20,7 @@
 #elif defined(SK_BUILD_FOR_UNIX)
 #include <GL/gl.h>
 #elif defined(SK_BUILD_FOR_MAC)
-#include <gl.h>
+#include <OpenGL/gl.h>
 #endif
 
 /*
@@ -224,7 +224,7 @@
     SkPaint paint;
 
     // create a surface for CPU rasterization
-    SkAutoTUnref<SkSurface> cpuSurface(SkSurface::NewRaster(canvas->imageInfo()));
+    sk_sp<SkSurface> cpuSurface(SkSurface::MakeRaster(canvas->imageInfo()));
 
     SkCanvas* offscreen = cpuSurface->getCanvas();
     offscreen->save();
@@ -232,7 +232,7 @@
     offscreen->drawPath(create_star(), paint);
     offscreen->restore();
 
-    SkAutoTUnref<SkImage> image(cpuSurface->newImageSnapshot());
+    sk_sp<SkImage> image = cpuSurface->makeImageSnapshot();
 
     int rotation = 0;
     while (!state.fQuit) { // Our application loop