Move some helper methods to DexRegisterLocation.

Test: test-art-host-gtest-stack_map_test
Change-Id: I0abab008159db023d531df69214cd3bb8c0639bd
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 4a53425..7a7a80e 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -3658,7 +3658,7 @@
           REQUIRES_SHARED(Locks::mutator_lock_) {
         bool found = false;
         for (size_t dex_reg = 0; dex_reg != number_of_dex_registers; ++dex_reg) {
-          DexRegisterLocation location = dex_register_map.GetDexRegisterLocation(dex_reg);
+          DexRegisterLocation location = dex_register_map[dex_reg];
           if (location.GetKind() == kind && static_cast<size_t>(location.GetValue()) == index) {
             visitor(ref, dex_reg, stack_visitor);
             found = true;