Remove instructions from dead blocks when building the dominator tree

We now remove the instructions to free up memory. We have to refactor
methods a little bit to avoid removing instructions as users twice,
since we do not support that.

Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Change-Id: Ia34c4a6af204952d295e5a2cb534115ced97ab07
2 files changed