getTile
Returns a Tile based on X, Y and Zoom This method is called by the Map in a synchronous manner, so all methods called from this will have to be fast and reliable to not slow anything down.
We always try to get a local tile first, and if it doesn't exist, we'll get it and save it for later use
Also be aware, that searching for usages on this method will not return any useful information regarding WHERE we're using it, as is called by Google only.
Return
Tile - from local storage or backend.
Parameters
x
X position of the tile
y
Y position of the tile
zoom
Zoom level of the tile