As suggested by dtoybox69@gmail.com, APPCOMMAND_LAUNCH_APP1 and APPCOMMAND_LAUNCH_APP2 could be customized and we don't know which application will be launched, so we should use a generic name like "LaunchApplication1" and "LaunchApplication2".
IE and Firefox use LaunchApplication1 and LaunchApplication2 for them because applications cannot detect they will launch which application. So, using abstract name might be better.
As suggested by dtoybox69@gmail.com,
APPCOMMAND_LAUNCH_APP1
andAPPCOMMAND_LAUNCH_APP2
could be customized and we don't know which application will be launched, so we should use a generic name like "LaunchApplication1" and "LaunchApplication2".See https://crbug.com/612743: