How Can I Convert Vector3 From Local To Global(World)?

I have the unity's old mouse look script that was in unity 4 maybe, and now im in unity 5.4 and having it, but the problem is its using this line of code:

transform.localEulerAngles = new Vector3(-RotationY,RotationX,0);

And the script works fine but in play mode it resets the X axis rotation of the character's head to 0 , so when i press play, the character's X axis rotation will be 0, and the character's head will look like the image bellow, so i want it to reset the X axis rotation in Global instead of Local, i know the problem is with the Vector3 resetting rotations to 0, but i want it to reset it to global rotation, any helps? :D