This is according to a sighting of a code commit in which it is referenced that Chrome for Android could come with a new button that when pressed, will close all tabs at once. You can see the button for yourself in the screenshot above where the icon is shown to the left of the screenshot. This button will appear when you pull up all the tabs that are currently open, where you can press the “+” button to open a new tab, or the three dots for more options/settings.
At the moment the current build of Chrome only features two buttons: the “+” button and the three dots. Unfortunately it is unclear when these changes are expected to make their way into Chrome for Android, but given the code commit hopefully it’ll show up in Chrome Canary soon, and then it will be made available to all users.