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

runtime/bin/gen_snapshot.cc

Index: runtime/bin/gen_snapshot.cc
===================================================================
--- runtime/bin/gen_snapshot.cc	(revision 22347)
+++ runtime/bin/gen_snapshot.cc	(working copy)
@@ -466,7 +466,10 @@
   // Note: We don't expect isolates to be created from dart code during
   // snapshot generation.
   if (!Dart_Initialize(NULL, NULL, NULL, NULL,
-                       NULL, NULL, NULL)) {
+                       DartUtils::OpenFile,
+                       DartUtils::ReadFile,
+                       DartUtils::WriteFile,
+                       DartUtils::CloseFile)) {
     Log::PrintErr("VM initialization failed\n");
     return 255;
   }