Operating system: Windows 7 (64 bit)
Graphics card: Radeon HD 8670D
Broken: 2.80, 69b2f5268114, blender2.7, 2019-02-10, as found on the splash screen
Short description of error
window_manager.invoke_popup() ignores preferences.view.ui_scale (window_manager.invoke_props_dialog() respects it).
In other words, the size of dialogs created with window_manager.invoke_popup() doesn't scale with the rest of the UI.
Exact steps for others to reproduce the error
Open the attached file
The size of the displayed dialogs (apart from the extra "OK" button) at a given UI scale should be the same, but it isn't.