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 2b48af202dbbf4498e861ec9c1c2278584697b20..58f1f8aea71cd1adcd6887959ac4a8cf74b61cda 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* GenerateSource();
+
   // 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.
@@ -2273,7 +2275,8 @@ class TokenStream : public Object {
   RawExternalTypedData* GetStream() const;
   void SetStream(const ExternalTypedData& stream) const;
 
-  RawString* GenerateSource() const;
+  RawString* GenerateSource(intptr_t start_tok_pos = 0,
+                            intptr_t end_tok_pos = -1) const;
   intptr_t ComputeSourcePosition(intptr_t tok_pos) const;
 
   RawString* PrivateKey() const;