Looks like a call to a physics test program is made here with the parameter "-game" to be "HL3" and "-open" to be something undefined, probably the name of the object to be tested.

The file was recently updated (February 3rd, 2015)

I'm usually searching through those files after every DOTA2 update since the Source2 implementation and I didn't notice that
reference yet but there are chances that this string is in there since the beginning and is just some legacy stuff.

E3 2015-Half Life 3!

Дали?Според мен ще си чакаме до Е3,по-рано изключено.

https://i.imgur.com/ArFmGXB.png

Също така:
https://m.facebook.com/Valve/photos/a.494482165147.300299.103632155147/103638145147/?type=1&source=48

Смениха снимката си за Фейсбук...

Three

Confirmed

HTC

Било е очевидно!