Fix deferred load errors / bug #26482

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/become.h"
@@ skipping 10918 matching lines @@
     Thread* thread = Thread::Current();
     Isolate* isolate = thread->isolate();
     Zone* zone = thread->zone();
     deferred_lib.SetLoadRequested();
     const GrowableObjectArray& pending_deferred_loads =
         GrowableObjectArray::Handle(
             isolate->object_store()->pending_deferred_loads());
     pending_deferred_loads.Add(deferred_lib);
     const String& lib_url = String::Handle(zone, deferred_lib.url());
     Dart_LibraryTagHandler handler = isolate->library_tag_handler();
+    Object& obj = Object::Handle(zone);
     {
       TransitionVMToNative transition(thread);
       Api::Scope api_scope(thread);
-      handler(Dart_kImportTag,
-              Api::NewHandle(thread, importer()),
-              Api::NewHandle(thread, lib_url.raw()));
+      obj = Api::UnwrapHandle(
+              handler(Dart_kImportTag,
+                      Api::NewHandle(thread, importer()),
+                      Api::NewHandle(thread, lib_url.raw())));
+    }
+    if (obj.IsError()) {
+      Exceptions::PropagateError(Error::Cast(obj));
     }
   } else {
     // Another load request is in flight.
     ASSERT(deferred_lib.LoadRequested());
   }
   return false;  // Load request not yet completed.
 }
 
 
 RawArray* LibraryPrefix::dependent_code() const {
@@ skipping 11677 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart