Update SkiaSDLExample to latest Ganesh interfaces.

Also updates SDL to 2.0.5.

Change-Id: I3a3c8f69360fc20a3d543c19dcf82dd3f42f1309
Reviewed-on: https://skia-review.googlesource.com/22204
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index d0bfa57..dc8cca0 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1598,6 +1598,21 @@
     }
   }
 
+  if (skia_enable_gpu && (is_linux || is_mac)) {
+    test_app("SkiaSDLExample") {
+      sources = [
+        "example/SkiaSDLExample.cpp",
+      ]
+      libs = []
+      include_dirs = []
+      deps = [
+        ":gpu_tool_utils",
+        ":skia",
+        "//third_party/libsdl",
+      ]
+    }
+  }
+
   if (is_android && defined(ndk) && ndk != "") {
     copy("gdbserver") {
       sources = [