Including a fix: object-macros.h needs to be the last include: otherwise
we'll have a problem when a file does this:

#include "object-macros.h"
#include "x.h" // x.h also includes object-macros.h

BUG=v8:5402

Review-Url: https://codereview.chromium.org/2623573003
Cr-Commit-Position: refs/heads/master@{#42187}