Turn CHECK()s into ASSERT()s.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index a53a196e54fac31d451d0d82f53e276e1b6b9bc2..c3dc8ac30ccef168e72aeb536d8b390077124801 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1695,9 +1695,10 @@ void LCodeGen::DoConstantT(LConstantT* instr) {
   AllowDeferredHandleDereference smi_check;
   if (instr->hydrogen()->HasObjectMap()) {
     Handle<Map> object_map = instr->hydrogen()->ObjectMap().handle();
-    CHECK(object->IsHeapObject());
-    CHECK(!object_map->is_stable() ||
-          *object_map == Handle<HeapObject>::cast(object)->map());
+    ASSERT(object->IsHeapObject());
+    ASSERT(!object_map->is_stable() ||
+           *object_map == Handle<HeapObject>::cast(object)->map());
+    USE(object_map);
   }
   __ Move(ToRegister(instr->result()), object);
 }