Remove generic call merge button.

We now use the same button component for merge. Formerly, it seems
that it was included in the "extra button row" to accomodate the
add and merge options both showing at the same time. Now, we handle
this as an additional scenario for the overflow menu button.

This is prework in order to be able to delete the extra button row,
and add a different "row" for the conferece call manager.

Bug: 15862303
Change-Id: I278ea17291d8daf3c5201116a10e3641b5deb4e1
7 files changed
tree: b2ca240c839f3fb13a0fdad35a0c9f34a4376c5f
  1. InCallUI/