Avoid re doing the look up for Occupancy from the dEdX tool if we have it already
requested to merge ATLAS-EGamma/athena:Electron_PID_try_to_avoid_recalc_of_occupancy_if_there into master
It seems in cases we call the occupancy calculation twice in the ElectronPID Tool. There is a tool that has a cache (via Write/Read Handle Put mechanism) , but since this is a private tool (so we have different instances of the tool and the of the cache it holds) we end up with two calls and 2 lookup in 2 caches.
In principle if we have the track level occupancy we can pass it (optionally) also down to the dEdX tool and avoid the 2nd call to the tool with same track as input and the relevant lookup . This MR tries this.
Mentining @sroe