Backport some work from sample to embedder:

runtime/embedders/android/graphics.h

 // 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.
 
 #ifndef EMBEDDERS_ANDROID_GRAPHICS_H_
 #define EMBEDDERS_ANDROID_GRAPHICS_H_
 
 #include <android_native_app_glue.h>
 #include <EGL/egl.h>
+#include <GLES2/gl2.h>
+#include <GLES2/gl2ext.h>
 
 #include "embedders/android/timer.h"
 
 class Graphics {
   public:
     Graphics(android_app* application, Timer* timer);
 
     const int32_t& height();
     const int32_t& width();
     int32_t Start();
     void Stop();
+    void SwapBuffers();
     int32_t Update();
+    void SetViewport(int left, int top, int width, int height);
+    int BuildProgram(const char* vertexShaderSource,
+                        const char* fragmentShaderSource) const;
+    int BuildShader(const char* source, GLenum shaderType) const;
 
   private:
     android_app* application_;
     Timer* timer_;
     int32_t width_, height_;
     EGLDisplay display_;
     EGLSurface surface_;
     EGLContext context_;
 };
 
 #endif  // EMBEDDERS_ANDROID_GRAPHICS_H_