Fix crash when posting a message to a send port with port id 0.

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 477d3b2bb03653093eecf465525ffc77e50499ed..e77c9c0876c098545de7ee4430d0a3414f05c86f 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -1609,6 +1609,9 @@ static uint8_t* allocator(uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
 
 
 DART_EXPORT bool Dart_Post(Dart_Port port_id, Dart_Handle handle) {
+  if (port_id == ILLEGAL_PORT) {
+    return false;
+  }
   Isolate* isolate = Isolate::Current();
   DARTSCOPE(isolate);
   const Object& object = Object::Handle(isolate, Api::UnwrapHandle(handle));
@@ -1622,6 +1625,11 @@ DART_EXPORT bool Dart_Post(Dart_Port port_id, Dart_Handle handle) {
 
 
 DART_EXPORT Dart_Handle Dart_NewSendPort(Dart_Port port_id) {
+  if (port_id == ILLEGAL_PORT) {

[zra, 2015/04/04 05:03:47]

Should this go after grabbing the current isolate so we don't try to allocate a
new error when there isn't one? That seems to be the pattern in other calls.

[Cutch, 2015/04/05 19:06:09]

Done.

+    return Api::NewError("%s: illegal port_id %" Pd64 ".",
+                         CURRENT_FUNC,
+                         port_id);
+  }
   Isolate* isolate = Isolate::Current();
   DARTSCOPE(isolate);
   CHECK_CALLBACK_STATE(isolate);