Snapshots: Add --extra-code flag to mksnapshot which lets you specify a file

src/snapshot-common.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 42 matching lines @@
     DeleteArray(str);
     return true;
   } else if (size_ > 0) {
     Deserialize(raw_data_, raw_size_);
     return true;
   }
   return false;
 }
 
 
+bool Snapshot::HaveASnapshotToStartFrom() {
+  return size_ != 0;
+}
+
+
 Handle<Context> Snapshot::NewContextFromSnapshot() {
   if (context_size_ == 0) {
     return Handle<Context>();
   }
   HEAP->ReserveSpace(new_space_used_,
                      pointer_space_used_,
                      data_space_used_,
                      code_space_used_,
                      map_space_used_,
                      cell_space_used_,
                      large_space_used_);
   SnapshotByteSource source(context_raw_data_,
                             context_raw_size_);
   Deserializer deserializer(&source);
   Object* root;
   deserializer.DeserializePartial(&root);
   CHECK(root->IsContext());
   return Handle<Context>(Context::cast(root));
 }
 
 } }  // namespace v8::internal