Revert of [snapshot] full setup delegate should also be able to deserialize.

src/setup-isolate.h

Index: src/setup-isolate.h
diff --git a/src/setup-isolate.h b/src/setup-isolate.h
index 1cdc9c9e76809e4df89b805641ad4bb97d46e5a9..2e56eaec64a2e374a1f6b2c91bf7d07103f07624 100644
--- a/src/setup-isolate.h
+++ b/src/setup-isolate.h
@@ -16,12 +16,11 @@
 // This class is an abstraction layer around initialization of components
 // that are either deserialized from the snapshot or generated from scratch.
 // Currently this includes builtins and interpreter bytecode handlers.
-// There are two implementations to choose from at link time:
+// There are three implementations to choose from (at link time):
 // - setup-isolate-deserialize.cc: always loads things from snapshot.
-// - setup-isolate-full.cc: loads from snapshot or bootstraps from scratch,
-//                          controlled by the |create_heap_objects| flag.
-// For testing, the implementation in setup-isolate-for-tests.cc can be chosen
-// to force the behavior of setup-isolate-full.cc at runtime.
+// - setup-isolate-full.cc: always generates things.
+// - setup-isolate-for-tests.cc: does the one or the other, controlled by
+//                               the |create_heap_objects| flag.
 //
 // The actual implementations of generation of builtins and handlers is in
 // setup-builtins-internal.cc and setup-interpreter-internal.cc, and is