Add a command line option to generate source code for a script

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 19934)
+++ runtime/vm/object.cc	(working copy)
@@ -5330,14 +5330,18 @@
 RawString* Script::Source() const {
   String& source = String::Handle(raw_ptr()->source_);
   if (source.IsNull()) {
-    const TokenStream& token_stream = TokenStream::Handle(tokens());
-    return token_stream.GenerateSource();
-  } else {
-    return raw_ptr()->source_;
+    return GenerateSource();
   }
+  return raw_ptr()->source_;
 }
 
 
+RawString* Script::GenerateSource() const {
+  const TokenStream& token_stream = TokenStream::Handle(tokens());
+  return token_stream.GenerateSource();
+}
+
+
 void Script::set_url(const String& value) const {
   StorePointer(&raw_ptr()->url_, value.raw());
 }