Steps to reproduce:
1. Open "BugDemo" case
2. Open "ExampleScene" scene
-- Notice that there are two canvases in hierarchy showing the issue
3. Try swapping Border with Fill places in hierarchy of Canvas parent object
-- This should change drawing order

Results: Canvas doesn't sort child objects when their Z positions are the same

Note: Does not reproduces on Unity 5.5.0a5. This issue needs to be investigated in 5.4.

Reproduced with: 5.4.0p1, 5.3.6f1, 5.3.5f1
Not reproducible with: 5.5.0a5