Some improvement to reg alloc.

Change-Id: If579a37791278500a7e5bc763f144c241f261920
diff --git a/compiler/optimizing/optimizing_unit_test.h b/compiler/optimizing/optimizing_unit_test.h
index 5b693dd..aae7f9b 100644
--- a/compiler/optimizing/optimizing_unit_test.h
+++ b/compiler/optimizing/optimizing_unit_test.h
@@ -46,7 +46,7 @@
                             size_t number_of_ranges,
                             ArenaAllocator* allocator,
                             int reg = -1) {
-  LiveInterval* interval = new (allocator) LiveInterval(allocator, Primitive::kPrimInt);
+  LiveInterval* interval = LiveInterval::MakeInterval(allocator, Primitive::kPrimInt);
   for (size_t i = number_of_ranges; i > 0; --i) {
     interval->AddRange(ranges[i - 1][0], ranges[i - 1][1]);
   }