Add VerfiedMethod to DexCompilationUnit.

Avoid some mutex locking and map lookups.

Change-Id: I8e0486af77e38dcd065569572a6b985eb57f4f63
diff --git a/compiler/dex/quick/gen_common.cc b/compiler/dex/quick/gen_common.cc
index d8b9869..746c1db 100644
--- a/compiler/dex/quick/gen_common.cc
+++ b/compiler/dex/quick/gen_common.cc
@@ -1133,8 +1133,7 @@
   // Note: currently type_known_final is unused, as optimizing will only improve the performance
   // of the exception throw path.
   DexCompilationUnit* cu = mir_graph_->GetCurrentDexCompilationUnit();
-  const MethodReference mr(cu->GetDexFile(), cu->GetDexMethodIndex());
-  if (!needs_access_check && cu_->compiler_driver->IsSafeCast(mr, insn_idx)) {
+  if (!needs_access_check && cu_->compiler_driver->IsSafeCast(cu, insn_idx)) {
     // Verifier type analysis proved this check cast would never cause an exception.
     return;
   }