opengles emulator: Fixed upside-down gl image

This fix performs a flip software copy to match our coords with those expected by the flinger.
We may think of a better implementation in the future.

Change-Id: Ic09a5d0e22f7e209b33c07c993a3d56e328dd3ed

tools/emulator/opengl/host/libs/libOpenglRender/WindowSurface.h

@@ -58,6 +58,7 @@ private:
     bool m_useEGLImage;
     bool m_useBindToTexture;
     FixedBuffer m_xferBuffer;
+    FixedBuffer m_xUpdateBuf;
 };
 
 typedef SmartPtr<WindowSurface> WindowSurfacePtr;