Simplify some DCHECKs.

R=sigurds@chromium.org

Change-Id: Iaabe863956bb59755af570cd031ab486f5fe3f20
Reviewed-on: https://chromium-review.googlesource.com/c/1460942Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59494}

src/compiler/js-native-context-specialization.cc

@@ -574,7 +574,6 @@ JSNativeContextSpecialization::InferHasInPrototypeChain(
     }
   }
   DCHECK_IMPLIES(all, !none);
-  DCHECK_IMPLIES(none, !all);
 
   if (all) return kIsInPrototypeChain;
   if (none) return kIsNotInPrototypeChain;
@@ -3132,7 +3131,7 @@ bool JSNativeContextSpecialization::CanTreatHoleAsUndefined(
 bool JSNativeContextSpecialization::ExtractReceiverMaps(
     Node* receiver, Node* effect, FeedbackNexus const& nexus,
     MapHandles* receiver_maps) {
-  DCHECK_EQ(0, receiver_maps->size());
+  DCHECK(receiver_maps->empty());
   if (nexus.IsUninitialized()) return true;
 
   // See if we can infer a concrete type for the {receiver}. Solely relying on