Add iOS support for SkiaSDLExample.

Change-Id: Ib8f4d6c41356cf0fe2e14b7bff7713d107eaa01f
Reviewed-on: https://skia-review.googlesource.com/40687
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/example/SkiaSDLExample.cpp b/example/SkiaSDLExample.cpp
index 3c4dccc..6525411 100644
--- a/example/SkiaSDLExample.cpp
+++ b/example/SkiaSDLExample.cpp
@@ -22,6 +22,8 @@
 #include <GL/gl.h>
 #elif defined(SK_BUILD_FOR_MAC)
 #include <OpenGL/gl.h>
+#elif defined(SK_BUILD_FOR_IOS)
+#include <OpenGLES/ES2/gl.h>
 #endif
 
 /*