This issue affected windows with JUCE titlebars. When dragging the
window back and forth between two displays with different DPI settings,
the window could sometimes end up with the wrong size.
It looks like setting new window bounds inside the WM_WINDOWPOSCHANGED
message was occasionally causing the system to lose track of the correct
scale for the window.
As a byproduct of this change, JUCE should no longer receive reentrant
calls to handleDPIChanging.