Update aosp/master LLVM for rebase to r222494.

Change-Id: Ic787f5e0124df789bd26f3f24680f45e678eef2d
diff --git a/lib/CodeGen/MachineDominators.cpp b/lib/CodeGen/MachineDominators.cpp
index 04c8ecb..df60cf3 100644
--- a/lib/CodeGen/MachineDominators.cpp
+++ b/lib/CodeGen/MachineDominators.cpp
@@ -35,6 +35,8 @@
 }
 
 bool MachineDominatorTree::runOnMachineFunction(MachineFunction &F) {
+  CriticalEdgesToSplit.clear();
+  NewBBs.clear();
   DT->recalculate(F);
 
   return false;