I don't get the same on my device, when I'm using debug (via the App Preview on my device) vs an installation. The App Preview is displaying it like I want to.
I have noticed that the App Preview must have some hardcoded options build in, e.g. it doesn't react to Fullscreen = false. Are there other harcoded options which I could maybe adopt to make my app display right?
My device is a Huawei Honor 7 Lite with Android Marshmallow, and I think it maybe related to the high resolution (1920x1080) since it displays fine on my other Android devices.
App via App Preview:
An clues as to get this working?
App Preview runs your app on the "native" webview. If you build with Crosswalk your app runs on top of the Crosswalk webview. There are some differences in the way fonts are sized between the Android 5+ native webviews and the Crosswalk webviews (has to do with how the screen size is judged). You can either apply an overall "uplift" to the size of the fonts (for example, by applying a rule to the body tag) or do all of your testing using the Debug tab, rather than App Preview. The Debug tab also uses a Crosswalk runtime to render your app.
Or, you can build without Crosswalk, which works great on Android 5+ devices, but is problematic on Android 4.x devices.
I'm not using Crosswalk.
I found the source of the problem. On My Huawei I can choose a simple screen, and this seems to affect html in general. Even this page has bigger fonts when enabling the simple screen. Well, that is my conclusion since it does not seem to affect native apps.
I just can't figure out why it looks fine when run via App Preview, though.