It sounds like you are changing the scene size width?
Most likely what is happening is: Chrome's responsive design mode is following the Viewport Width mobile option. If it is set to "Document Width," the default, then this will effectively scale your document to fit. The viewport width in mobile terms is basically your window size.
You should probably change this to "Device width" so that this matches physical pixels. You could also choose "Not set" which lets a device decide something reasonable.
You'll probably also want to check "Initial scale 1.0" as Chrome seems to also scale your document down independently of the viewport size to fit.