Fix up the layouttest situation after r185322
It's difficult to maintain WK1 and WK2 results on a per-platform basis. So to resolve this, let's split out the IDB specific constructors (that will only show up on WK2 on any given platform) into their own test.
Created attachment 254522 [details]
Comment on attachment 254522 [details]
rs=me, please wait for Mac testers to finish.