Expose set_source service command for functions

runtime/vm/parser.h

Index: runtime/vm/parser.h
diff --git a/runtime/vm/parser.h b/runtime/vm/parser.h
index 1fb7f89e56af89789d16482373df99a3d40f810c..e95104668394f5fb51d8106fbc586e6759b019d1 100644
--- a/runtime/vm/parser.h
+++ b/runtime/vm/parser.h
@@ -221,6 +221,10 @@ class Parser : public ValueObject {
   // given static field.
   static ParsedFunction* ParseStaticFieldInitializer(const Field& field);
 
+  // Returns a RawFunction or RawError.
+  static RawObject* ParseFunctionFromSource(const Class& owning_class,
+                                            const String& source);
+
   // Parse a function to retrieve parameter information that is not retained in
   // the dart::Function object. Returns either an error if the parse fails
   // (which could be the case for local functions), or a flat array of entries