Second step towards loading the core library scripts directly from the sources

runtime/bin/dartutils.h

Index: runtime/bin/dartutils.h
===================================================================
--- runtime/bin/dartutils.h	(revision 22375)
+++ runtime/bin/dartutils.h	(working copy)
@@ -108,6 +108,10 @@
   static Dart_Handle CanonicalizeURL(CommandLineOptions* url_mapping,
                                      Dart_Handle library,
                                      const char* url_str);
+  static void* OpenFile(const char* name, bool write);
+  static void ReadFile(const uint8_t** data, intptr_t* file_len, void* stream);
+  static void WriteFile(const void* buffer, intptr_t num_bytes, void* stream);
+  static void CloseFile(void* stream);
   static Dart_Handle ReadStringFromFile(const char* filename);
   static Dart_Handle LibraryTagHandler(Dart_LibraryTag tag,
                                        Dart_Handle library,