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

src/snapshot.h

 // 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 22 matching lines @@
 namespace v8 {
 namespace internal {
 
 class Snapshot {
  public:
   // Initialize the VM from the given snapshot file. If snapshot_file is
   // NULL, use the internal snapshot instead. Returns false if no snapshot
   // could be found.
   static bool Initialize(const char* snapshot_file = NULL);
 
+  static bool HaveASnapshotToStartFrom();
+
   // Create a new context using the internal partial snapshot.
   static Handle<Context> NewContextFromSnapshot();
 
   // Returns whether or not the snapshot is enabled.
   static bool IsEnabled() { return size_ != 0; }
 
   // Write snapshot to the given file. Returns true if snapshot was written
   // successfully.
   static bool WriteToFile(const char* snapshot_file);
 
@@ skipping 29 matching lines @@
   static const int context_raw_size_;
 
   static bool Deserialize(const byte* content, int len);
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(Snapshot);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SNAPSHOT_H_