Extract localStorage tests out into a helper method; use in getCurrentValue()
Extract localStorage tests out into a helper method; use in getCurrentValue()

1. Extract the tests for whether or not we have workable localStorage out into
   a helper method, so it can be more easily reused
2. Use it in getCurrentValue() too, for the same reasons, as suggested in code
   review

GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust