Changes to prepare for allowing script snapshots to be taken after running the main application

runtime/vm/snapshot.h

Index: runtime/vm/snapshot.h
diff --git a/runtime/vm/snapshot.h b/runtime/vm/snapshot.h
index 6d1b7184a81a3fcb18e10e7dd30ab8ba91cd58a2..d58490e881d3f8aaf096578aa2681da172d060c4 100644
--- a/runtime/vm/snapshot.h
+++ b/runtime/vm/snapshot.h
@@ -838,6 +838,7 @@ class SnapshotWriter : public BaseWriter {
   friend class RawArray;
   friend class RawClass;
   friend class RawClosureData;
+  friend class RawContextScope;
   friend class RawExceptionHandlers;
   friend class RawGrowableObjectArray;
   friend class RawImmutableArray;