Renamed "symbols" to "internalized strings" throughout the code base,

src/serialize.cc

Index: src/serialize.cc
diff --git a/src/serialize.cc b/src/serialize.cc
index eeb180ac324783dd34cfa3335bea04ba068f8c95..10873b9188a03e8ff99aee16ce1c2893e0a76c85 100644
--- a/src/serialize.cc
+++ b/src/serialize.cc
@@ -1355,9 +1355,9 @@ void PartialSerializer::SerializeObject(
   // should go through the root array or through the partial snapshot cache.
   // If this is not the case you may have to add something to the root array.
   ASSERT(!startup_serializer_->address_mapper()->IsMapped(heap_object));
-  // All the symbols that the partial snapshot needs should be either in the
-  // root table or in the partial snapshot cache.
-  ASSERT(!heap_object->IsSymbol());
+  // All the internalized strings that the partial snapshot needs should be
+  // either in the root table or in the partial snapshot cache.
+  ASSERT(!heap_object->IsInternalizedString());
 
   if (address_mapper_.IsMapped(heap_object)) {
     int space = SpaceOfObject(heap_object);