Code review comment for lp:~vanvugt/unity/fix-1043260-6.0

Warning:
This fix will slow down active blur a little.

If we desperately want to maintain performance then I suggest either:
  (a) Don't approve it and let the bugs slip into quantal b2; or
  (b) Ask a Nux/Unity expert to look at unity-shared/BackgroundEffectHelper.cpp and rewrite it to only do one blur (used by all geos) per frame.