Refactored Android samples / embedder.

samples/android_sample/assets/dart/android_extension.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library android_extension;
 
-import "dart-ext:android_extension";
-
 // The simplest way to call native code: top-level functions.
 int systemRand() native "SystemRand";
 void systemSrand(int seed) native "SystemSrand";
 void log(String what) native "Log";
 
 // EGL functions.
 void eglSwapBuffers() native "EGLSwapBuffers";
 
 // GL functions.
 void glAttachShader(int program, int shader) native "GLAttachShader";
@@ skipping 122 matching lines @@
 }
 
 var gl = new WebGLRenderingContext();
 
 //------------------------------------------------------------------
 // Simple audio support.
 
 void playBackground(String path) native "PlayBackground";
 void stopBackground() native "StopBackground";