Add markPreviousEnd to header
Add markPreviousEnd to header

Summary: Add to header so the begining of the device log can be controlled.

Reviewed By: sigmix

Differential Revision: D3772039

fbshipit-source-id: 8640408cd8584ba63c3843c35d08b0e3cf5272cf

bootstraponline/FBSimulatorControl,plu/FBSimulatorControl,StevenUpForever/FBSimulatorControl,facebook/FBSimulatorControl,ichu501/FBSimulatorControl,facebook/FBSimulatorControl,bootstraponline/FBSimulatorControl,facebook/FBSimulatorControl,plu/FBSimulatorControl,StevenUpForever/FBSimulatorControl,bootstraponline/FBSimulatorControl,StevenUpForever/FBSimulatorControl,StevenUpForever/FBSimulatorControl,facebook/FBSimulatorControl,bootstraponline/FBSimulatorControl,plu/FBSimulatorControl,plu/FBSimulatorControl,facebook/FBSimulatorControl