When using Unity Perforce support, some changes to the scene file which cause it to be dirtied do not check the file out from Perforce on save. It seems like this only happens the first time it's changed, if the field is changed a second time, it seems to be being caught.

This seems to happen on inspector fields which have Property Drawers drawing them, or on other fields in the MB (even if they don't have Property Drawers).

To reproduce:
1. Set up perforce
2. Checked in attached project
3. Open up TestScene - must not be checked out in Perforce
4. Select "Perforce Tester" object in scene hierarchy
5. In inspector, change value for field "Prop Drawer" from 0 to some value.
6. Note the scene becomes flagged in the title bar as dirty (has the *)
7. Save scene
8. Notice that scene is not checked out

Expected result: scene which has been modified should be checked out from Perforce

Reproducible: 5.6.0a3, 5.4.2p3, 5.3.7f1

Note: Changing the field a second time and re-saving the scene does cause the scene to be checked out in this particular example, but I have some reports that changing again and re-saving in a more complex scene + property drawer combination still causes it to not be checked out on save.