Computer Configuration > Administrative Templates > Google Chrome > Idle Browser Actions
Both
HKLM\Software\Policies\Google\Chrome
Triggers an action when the computer is idle. If this policy is set, it specifies the length of time without user input (in minutes) before the browser runs actions configured via the IdleTimeoutActions policy. If this policy is not set, no action will be ran. The minimum threshold is 1 minute. "User input" is defined by Operating System APIs, and includes things like moving the mouse or typing on the keyboard.