Add a standalone SkyShell.apk for testing

sky/shell/sky_main.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sky/compositor/rasterizer.h"
+#ifndef SKY_SHELL_SKY_MAIN_H_
+#define SKY_SHELL_SKY_MAIN_H_
+
+#include <jni.h>
 
 namespace sky {
+namespace shell {
 
-Rasterizer::Rasterizer() {
-}
+bool RegisterSkyMain(JNIEnv* env);
 
-Rasterizer::~Rasterizer() {
-}
+}  // namespace shell
+}  // namespace sky
 
-}  // namespace sky
+#endif  // SKY_SHELL_SKY_MAIN_H_