Bit of a cleanup.

Change-Id: I814ab7e55119a28bd52a8da7f21c03ff44c73e33
Move this to its own method.

Change-Id: Ief8356bc8e0d3d791c97849b8b00ece4ede0b803
Special case for formula cell fill down for quicker filling.

Change-Id: Ia03aa4c042b22551deacf4d7a58c9492a0a13a66