ART: More header cleanups

Clean up some more includes. Move some -inls from object-inl to
object-refvisitor-inl. Fix up transitives.

Test: m test-art-host
Change-Id: I0e3e268d95a1c71b0a80fc963d13d191a97b2283
diff --git a/runtime/mirror/string.cc b/runtime/mirror/string.cc
index de0e75b..2b31aef 100644
--- a/runtime/mirror/string.cc
+++ b/runtime/mirror/string.cc
@@ -18,6 +18,7 @@
 
 #include "arch/memcmp16.h"
 #include "array.h"
+#include "base/array_ref.h"
 #include "class-inl.h"
 #include "gc/accounting/card_table-inl.h"
 #include "handle_scope-inl.h"