Add ability for Function to generate source

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 3610f928be954e20f6bcbe1bbefeb9d3f121b35e..e014f0f7067f532417db7760909ad1494051da43 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -1443,6 +1443,8 @@ class Function : public Object {
   RawString* QualifiedUserVisibleName() const;
   virtual RawString* DictionaryName() const { return name(); }
 
+  RawString* GetSource();
+
   // Build a string of the form 'C<T, R>(T, {b: B, c: C}) => R' representing the
   // internal signature of the given function. In this example, T and R are
   // type parameters of class C, the owner of the function.
@@ -2368,7 +2370,8 @@ class Script : public Object {
   void Tokenize(const String& private_key) const;
 
   RawString* GetLine(intptr_t line_number) const;
-
+  RawString* GetSnippet(intptr_t from_token_pos,
+                        intptr_t to_token_pos) const;
   RawString* GetSnippet(intptr_t from_line,
                         intptr_t from_column,
                         intptr_t to_line,