Add metric for class names hashes

Summary: This new metric will let us spot quickly if the InterDexPass made any changes, across two builds, in which classes got put into what dexes in what order, in the most important root store.

Reviewed By: itang00

Differential Revision: D67541817

fbshipit-source-id: 83c13452b80dadeca4fc069f47e06b7dbed3061d

opt/interdex/InterDexPass.cpp

@@ -209,6 +209,11 @@ void InterDexPass::run_pass(
     mgr.set_metric(key_prefix + "scroll", info.scroll);
     mgr.set_metric(key_prefix + "background", info.background);
     mgr.set_metric(key_prefix + "betamap_ordered", info.betamap_ordered);
+    size_t hash{0};
+    for (auto* cls : dexen[i]) {
+      boost::hash_combine(hash, cls->get_name()->str());
+    }
+    mgr.set_metric(key_prefix + "class_names_hash", hash);
   }
 
   auto final_scope = build_class_scope(stores);