Rearrange narrowing checks in initialization to be a different form of step
rather than a post-processing action, so we can support inserting these checks
at stages other than the end of the initialization. No functionality change
intended.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191146 91177308-0d34-0410-b5e6-96231b3b80d8