[REG 5.3->5.4] OS X: changing QMainWindow's min width and resizing causes stretching of contents on Mac, in Qt 5.4

This problem ONLY occurs on Mac and Qt 5.4
Building application with Qt 5.4 when you expand the width of a window the contents are stretched when the call to the setMinimumWidth() or the resize() call is made. This does NOT occur on Qt 5.3.
See attachments that show the window after each step in the debugger.
Attached zip contains the sample project to reproduce the problem.