Google has now published an official extension: 'Go Back With Backspace', to re-enable the backspace button as the hotkey for 'back'.
Re-enables the backspace key as a back navigation button (except when
writing text). Go back with the backspace button! This extension
re-enables the backspace key as a back navigation button -- except if
you're writing text.
Before Chrome 52, the backspace key navigated back (if you weren't
writing text). Many people lost their progress while working online by
accidentally pressing backspace and leaving a page -- so we removed
the feature from Chrome, and created this extension for those who
prefer the old behavior.
This extension can't restore backspace on certain special pages, for
example any of the "chrome://" pages such as Settings or Extensions.
About the "all sites" permission: In order to capture backspace on
every page, the extension needs to install a little piece of code on
each one. It does nothing else with the the page, its information, or