One of the most annoying things I encounter on a daily basis is constantly having to reset the zoom of the chrome device emulator.
For whatever reason, each time I change the device selection, the zoom changes from 100% to the "Fit to Window" size, which is always less than 100% and renders the page and text so tiny its unusable.
I've seen the "Edit" menu under the device listing, and this is where I would expect to find the setting to always default the zoom to 100%, however, I'm not seeing it there. What am I missing?
I had this problem for a while. Go to the right top menu as you see in the picture. Click on "Reset to defaults". It worked for me.
In the same menu where you are resetting the zoom percentage (the "Edit" menu you mentioned), you will see an option called "Auto-adjust zoom". Uncheck that option and set your zoom to 100%. 
来源：https://stackoverflow.com/questions/46813688/chrome-responsive-emulator-how-to-default-zoom-to-100