ApiVisualEditor: Separate save/diff switch case

They no longer overlap (except for 3 lines of code). The
double switch case for save/diff 90% of the body being if-save
and elseif-diff doesn't make sense.

Change-Id: Ic6f014393e72901bb5ab4449d946d94b87429e52
Merge "ApiVisualEditor: Separate save/diff switch case"