Computer Configuration > Administrative Templates > Google Chrome
Both
HKLM\Software\Policies\Google\Chrome
Setting the policy to Enabled or leaving it unset means Chrome can display, and users can open, file selection dialogs. Setting the policy to Disabled means that whenever users perform actions provoking a file selection dialog, such as importing bookmarks, uploading files, and saving links, a message appears instead. The user is assumed to have clicked Cancel on the file selection dialog.