Store embed-script flag as metadata into snapshot blob.

src/snapshot-external.cc

Index: src/snapshot-external.cc
diff --git a/src/snapshot-external.cc b/src/snapshot-external.cc
index 2fda57125220085a12ff0bf78224ab5d7ff72ec5..f26a5a1c18dba7a2b43410e352778a1bf179d4b5 100644
--- a/src/snapshot-external.cc
+++ b/src/snapshot-external.cc
@@ -26,9 +26,7 @@ void SetSnapshotFromFile(StartupData* snapshot_blob) {
   DCHECK(snapshot_blob->data);
   DCHECK(snapshot_blob->raw_size > 0);
   DCHECK(!external_startup_blob.data);
-  // Validate snapshot blob.
-  DCHECK(!Snapshot::ExtractStartupData(snapshot_blob).is_empty());
-  DCHECK(!Snapshot::ExtractContextData(snapshot_blob).is_empty());
+  DCHECK(Snapshot::SnapshotIsValid(snapshot_blob));
   external_startup_blob = *snapshot_blob;
 }