fix Corrupted graphics while playing You Tube on orientation change

    // redraw the screen entirely...

    glDisable(GL_TEXTURE_EXTERNAL_OES);

    glDisable(GL_TEXTURE_2D);

    glDisable(GL_SCISSOR_TEST);

    glClearColor(0,0,0,1);

    glClear(GL_COLOR_BUFFER_BIT);

    glEnable(GL_SCISSOR_TEST);

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();

    const Vector< sp<LayerBase> >& layers(mVisibleLayersSortedByZ);