Make common BitVector operations inline-able.

Change-Id: Ie25de4fae56c6712539f04172c42e3eff57df7ca
diff --git a/compiler/utils/arena_bit_vector.cc b/compiler/utils/arena_bit_vector.cc
index 39f7d18..de35f3d 100644
--- a/compiler/utils/arena_bit_vector.cc
+++ b/compiler/utils/arena_bit_vector.cc
@@ -16,11 +16,12 @@
 
 #include "arena_allocator.h"
 #include "arena_bit_vector.h"
+#include "base/allocator.h"
 
 namespace art {
 
 template <typename ArenaAlloc>
-class ArenaBitVectorAllocator : public Allocator {
+class ArenaBitVectorAllocator FINAL : public Allocator {
  public:
   explicit ArenaBitVectorAllocator(ArenaAlloc* arena) : arena_(arena) {}
   ~ArenaBitVectorAllocator() {}
@@ -37,7 +38,7 @@
   static void operator delete(void* p) {}  // Nop.
 
  private:
-  ArenaAlloc* arena_;
+  ArenaAlloc* const arena_;
   DISALLOW_COPY_AND_ASSIGN(ArenaBitVectorAllocator);
 };