Index is Index=Var+Const ==>
    set Index=Var, Offset+=(Const<<Shift)
  Index is Index=Const+Var ==>
    set Index=Var, Offset+=(Const<<Shift)
  Index is Index=Var-Const ==>
    set Index=Var, Offset-=(Const<<Shift)
BUG=none
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/2084793002 .