Rearrange Dom unittest to accommodate multiple tests

I've taken the approach from the LoopInfo test:

* Rather than running in the pass manager just build the analyses manually
* Split out the common parts (makeLLVMModule, runWithDomTree) into helpers

Differential Revision: https://reviews.llvm.org/D33617

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304061 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed