Add Dart API method Dart_SetPersistentHandle to enable setting the value of

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
===================================================================
--- runtime/vm/dart_api_impl.cc	(revision 31439)
+++ runtime/vm/dart_api_impl.cc	(working copy)
@@ -578,6 +578,25 @@
   return reinterpret_cast<Dart_PersistentHandle>(new_ref);
 }
 
+
+DART_EXPORT Dart_Handle Dart_SetPersistentHandle(Dart_PersistentHandle obj1,
+                                                 Dart_Handle obj2) {
+  Isolate* isolate = Isolate::Current();
+  DARTSCOPE(isolate);
+  ApiState* state = isolate->api_state();
+  ASSERT(state != NULL);
+  if (!state->IsValidPersistentHandle(obj1)) {

[Ivan Posva, 2014/01/03 18:21:21]

In other places we just assert on this instead of raising an API error. This
call should not be special, so we should make it consistent, by either changing
this to an ASSERT or throwing API errors in the other places such as
Dart_HandleFromPersistent for example.

[siva, 2014/01/03 18:33:49]

Done.

+    return Api::NewError(
+        "%s expects argument 'obj1' to be a persistent handle.",
+        CURRENT_FUNC);
+  }
+  const Object& obj2_ref = Object::Handle(isolate, Api::UnwrapHandle(obj2));
+  PersistentHandle* obj1_ref = Api::UnwrapAsPersistentHandle(obj1);
+  obj1_ref->set_raw(obj2_ref);
+  return Api::Success();

[Ivan Posva, 2014/01/03 18:21:21]

Then you can also change the signature of the function to be void. As you will
never have an error returned.

[siva, 2014/01/03 18:33:49]

Done.

+}
+
+
 static Dart_WeakPersistentHandle AllocateFinalizableHandle(
     Isolate* isolate,
     FinalizablePersistentHandles* handles,