Optimizing: Move GraphChecker memory allocations to arena.

Bug: 18120045
Change-Id: I3934158e6ea4868d9baa1dfcc53b603ca6c521e2
diff --git a/runtime/base/arena_allocator.h b/runtime/base/arena_allocator.h
index 47cd8b5..004895a 100644
--- a/runtime/base/arena_allocator.h
+++ b/runtime/base/arena_allocator.h
@@ -105,6 +105,7 @@
   kArenaAllocStackMapStream,
   kArenaAllocCodeGenerator,
   kArenaAllocParallelMoveResolver,
+  kArenaAllocGraphChecker,
   kNumArenaAllocKinds
 };