Code review comment for lp:~vanvugt/mir/bypass

When testing with ppa:mir-team/qa-testing I'm seeing a ~50% drop in framerates when running glmark2. Unity otherwise seems to run with no perceptible performance hit and is stable.

From archive:

=======================================================
    glmark2 2012.08
=======================================================
    OpenGL Information
    GL_VENDOR: Intel Open Source Technology Center
    GL_RENDERER: Mesa DRI Intel(R) Ironlake Mobile
    GL_VERSION: 2.1 Mesa 9.2.0-devel
=======================================================
[build] use-vbo=false: FPS: 113 FrameTime: 8.850 ms
[build] use-vbo=true: FPS: 215 FrameTime: 4.651 ms
[texture] texture-filter=nearest: FPS: 280 FrameTime: 3.571 ms
[texture] texture-filter=linear: FPS: 302 FrameTime: 3.311 ms
[texture] texture-filter=mipmap: FPS: 276 FrameTime: 3.623 ms
[shading] shading=gouraud: FPS: 248 FrameTime: 4.032 ms
[shading] shading=blinn-phong-inf: FPS: 200 FrameTime: 5.000 ms
[shading] shading=phong: FPS: 169 FrameTime: 5.917 ms
[bump] bump-render=high-poly: FPS: 105 FrameTime: 9.524 ms
[bump] bump-render=normals: FPS: 244 FrameTime: 4.098 ms
[bump] bump-render=height: FPS: 251 FrameTime: 3.984 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 134 FrameTime: 7.463 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 66 FrameTime: 15.152 ms
[pulsar] light=false:quads=5:texture=false: FPS: 222 FrameTime: 4.505 ms

From PPA:

=======================================================
    glmark2 2012.08
=======================================================
    OpenGL Information
    GL_VENDOR: Intel Open Source Technology Center
    GL_RENDERER: Mesa DRI Intel(R) Ironlake Mobile
    GL_VERSION: 2.1 Mesa 9.2.0-devel
=======================================================
[build] use-vbo=false: FPS: 114 FrameTime: 8.772 ms
[build] use-vbo=true: FPS: 116 FrameTime: 8.621 ms
[texture] texture-filter=nearest: FPS: 120 FrameTime: 8.333 ms
[texture] texture-filter=linear: FPS: 118 FrameTime: 8.475 ms
[texture] texture-filter=mipmap: FPS: 118 FrameTime: 8.475 ms
[shading] shading=gouraud: FPS: 101 FrameTime: 9.901 ms
[shading] shading=blinn-phong-inf: FPS: 117 FrameTime: 8.547 ms
[shading] shading=phong: FPS: 105 FrameTime: 9.524 ms
[bump] bump-render=high-poly: FPS: 90 FrameTime: 11.111 ms
[bump] bump-render=normals: FPS: 120 FrameTime: 8.333 ms
[bump] bump-render=height: FPS: 117 FrameTime: 8.547 ms
[effect2d] kernel=0,1,0;1,-4,1;0,1,0;: FPS: 102 FrameTime: 9.804 ms
[effect2d] kernel=1,1,1,1,1;1,1,1,1,1;1,1,1,1,1;: FPS: 59 FrameTime: 16.949 ms
[pulsar] light=false:quads=5:texture=false: FPS: 116 FrameTime: 8.621 ms

(both crash after pulsar due to bug 1203742)