Fix up code warning and errors

Discovered by new LLVM rebase.

Clean up, no functionality change.

Test: build
Bug: 37752547
Change-Id: I7df6097706e0772226dcb07611e7d044a6085421
diff --git a/compiler/utils/swap_space.h b/compiler/utils/swap_space.h
index c286b82..0ff9fc6 100644
--- a/compiler/utils/swap_space.h
+++ b/compiler/utils/swap_space.h
@@ -78,7 +78,7 @@
     mutable FreeByStartSet::const_iterator free_by_start_entry;
   };
   struct FreeBySizeComparator {
-    bool operator()(const FreeBySizeEntry& lhs, const FreeBySizeEntry& rhs) {
+    bool operator()(const FreeBySizeEntry& lhs, const FreeBySizeEntry& rhs) const {
       if (lhs.size != rhs.size) {
         return lhs.size < rhs.size;
       } else {