[snapshot] support including templates in the snapshot.

src/heap/heap-inl.h

Index: src/heap/heap-inl.h
diff --git a/src/heap/heap-inl.h b/src/heap/heap-inl.h
index 4b39da0d43d001b24fa11b50b412c269c769a090..a0a696f78ce3cf064c348f0747cd0c1453be714f 100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -732,6 +732,11 @@ int Heap::GetNextTemplateSerialNumber() {
   return next_serial_number;
 }
 
+void Heap::SetSerializedTemplates(FixedArray* templates) {
+  DCHECK_EQ(empty_fixed_array(), serialized_templates());
+  set_serialized_templates(templates);
+}
+
 AlwaysAllocateScope::AlwaysAllocateScope(Isolate* isolate)
     : heap_(isolate->heap()) {
   heap_->always_allocate_scope_count_.Increment(1);