Initial gyp files for SDL

gyp/sdl.gyp

Index: gyp/sdl.gyp
diff --git a/gyp/sdl.gyp b/gyp/sdl.gyp
new file mode 100644
index 0000000000000000000000000000000000000000..7e0e13da5d8de4583c6e2f8f6b6a99a3f328247c
--- /dev/null
+++ b/gyp/sdl.gyp
@@ -0,0 +1,15 @@
+# Copyright 2015 Google Inc.
+#
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+# A simple gyp file to generate SDL for internal purposes
+{
+  'variables': {
+    'base_dir%': '../third_party/libsdl',
+    'src_dir%': '../third_party/externals/sdl',
+    'skia_warnings_as_errors': 0,
+  },
+  'includes': [
+    '../third_party/libsdl/sdl.gypi',
+  ],
+}