VM: Save one bool when serializing library prefixes.

runtime/vm/raw_object_snapshot.cc

Index: runtime/vm/raw_object_snapshot.cc
diff --git a/runtime/vm/raw_object_snapshot.cc b/runtime/vm/raw_object_snapshot.cc
index f345a19deba1972574eaaeb0291e4163b803c7d3..d5fb5cf568ef5643dbd1b2c4b982338ee49f2e52 100644
--- a/runtime/vm/raw_object_snapshot.cc
+++ b/runtime/vm/raw_object_snapshot.cc
@@ -1189,7 +1189,7 @@ RawLibraryPrefix* LibraryPrefix::ReadFrom(SnapshotReader* reader,
                          reader->Read<int16_t>());
   prefix.StoreNonPointer(&prefix.raw_ptr()->is_deferred_load_,
                          reader->Read<bool>());
-  prefix.StoreNonPointer(&prefix.raw_ptr()->is_loaded_, reader->Read<bool>());
+  prefix.StoreNonPointer(&prefix.raw_ptr()->is_loaded_, false);
 
   // Set all the object fields.
   READ_OBJECT_FIELDS(prefix,
@@ -1220,7 +1220,6 @@ void RawLibraryPrefix::WriteTo(SnapshotWriter* writer,
   // Write out all non object fields.
   writer->Write<int16_t>(ptr()->num_imports_);
   writer->Write<bool>(ptr()->is_deferred_load_);
-  writer->Write<bool>(ptr()->is_loaded_);
 
   // Write out all the object pointer fields.
   SnapshotWriterVisitor visitor(writer, kAsReference);