SnapshotCreator: start from existing snapshot if we have one

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 866a0bc22441e84f5339397ba42f9ce2c190ea44..063cfa75bbd5e6bded8254dc0e08bb8db9320cd2 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -515,7 +515,15 @@ SnapshotCreator::SnapshotCreator(intptr_t* external_references,
     internal_isolate->set_snapshot_blob(existing_snapshot);
     i::Snapshot::Initialize(internal_isolate);
   } else {
-    internal_isolate->Init(nullptr);
+    // If we have a snapshot, use it for bootstrapping; otherwise start
+    // from scratch.
+    const StartupData* snapshot_blob = i::Snapshot::DefaultSnapshotBlob();

[Yang, 2017/03/07 11:28:11]

We could also make this the default parameter for existing_snapshot?

[Jakob Kummerow, 2017/03/07 12:39:15]

Done.

+    if (snapshot_blob != nullptr && snapshot_blob->raw_size > 0) {
+      internal_isolate->set_snapshot_blob(snapshot_blob);
+      i::Snapshot::Initialize(internal_isolate);
+    } else {
+      internal_isolate->Init(nullptr);
+    }
   }
   data_ = data;
 }