Fix cpplint whitespace/comments issues

Change-Id: Iae286862c85fb8fd8901eae1204cd6d271d69496
diff --git a/compiler/dex/arena_allocator.h b/compiler/dex/arena_allocator.h
index 3bd733e..e8e2c02 100644
--- a/compiler/dex/arena_allocator.h
+++ b/compiler/dex/arena_allocator.h
@@ -86,7 +86,7 @@
      explicit MemStats(const ArenaAllocator &arena) : arena_(arena) {}
   private:
     const ArenaAllocator &arena_;
-}; // MemStats
+};  // MemStats
 
 }  // namespace art