ART: Use utils.h::RoundUp instead of explicit bit-fiddling

Change-Id: I249a2cfeb044d3699d02e13d42b8e72518571640
diff --git a/compiler/utils/arena_allocator.h b/compiler/utils/arena_allocator.h
index 18a5bce..032eabc 100644
--- a/compiler/utils/arena_allocator.h
+++ b/compiler/utils/arena_allocator.h
@@ -23,6 +23,7 @@
 #include "base/macros.h"
 #include "base/mutex.h"
 #include "mem_map.h"
+#include "utils.h"
 
 namespace art {
 
@@ -155,7 +156,7 @@
     if (UNLIKELY(running_on_valgrind_)) {
       return AllocValgrind(bytes, kind);
     }
-    bytes = (bytes + 3) & ~3;
+    bytes = RoundUp(bytes, 4);
     if (UNLIKELY(ptr_ + bytes > end_)) {
       // Obtain a new block.
       ObtainNewArenaForAllocation(bytes);