State a fixed order for modifiers in the Shorcuts Helper

The current implementation takes the modifiers as stores in a
SparseArray, indexed by their KeyCode so they are showing up in
KeyCode order on the helper. We want to force order them into
something that makes more sense.

Bug: 29545953
Change-Id: Iad9b8a014075afdf9cf911c6393efde2ef9a7640