Pivot offset over the X axis is affected by particle size.

Repro steps:
1. Open Scene1 from attached project.
2. Select the ParticleSystem in the hierarchy.
3. Change the pivot offset on Y - observe the distance the particle is moved.
4. Change the pivot offset on X - observe how a larger number needs to be entered.
5. Change the particle size and observe the pivot change.

Expected outcome: size of the particle to not affect the offset.

Notes:
- Regressions in b22, most likely due to fix for 793101
- Old particles seem to upgrade fine, but new ones created in b22 onward show this behavior.