Make the "sticky error" an Error instead of a String.

runtime/vm/object_store.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_OBJECT_STORE_H_
 #define VM_OBJECT_STORE_H_
 
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 237 matching lines @@
   void set_registered_libraries(const Library& value) {
     registered_libraries_ = value.raw();
   }
 
   RawArray* pending_classes() const { return pending_classes_; }
   void set_pending_classes(const Array& value) {
     ASSERT(!value.IsNull());
     pending_classes_ = value.raw();
   }
 
-  RawString* sticky_error() const { return sticky_error_; }
-  void set_sticky_error(const String& value) {
+  RawError* sticky_error() const { return sticky_error_; }
+  void set_sticky_error(const Error& value) {
     ASSERT(!value.IsNull());
     sticky_error_ = value.raw();
   }
 
   RawBool* true_value() const { return true_value_; }
   void set_true_value(const Bool& value) { true_value_ = value.raw(); }
 
   RawBool* false_value() const { return false_value_; }
   void set_false_value(const Bool& value) { false_value_ = value.raw(); }
 
@@ skipping 66 matching lines @@
   RawBool* false_value_;
   RawArray* empty_array_;
   RawArray* symbol_table_;
   RawArray* canonical_type_arguments_;
   RawLibrary* core_library_;
   RawLibrary* core_impl_library_;
   RawLibrary* native_wrappers_library_;
   RawLibrary* root_library_;
   RawLibrary* registered_libraries_;
   RawArray* pending_classes_;
-  RawString* sticky_error_;
+  RawError* sticky_error_;
   RawContext* empty_context_;
   RawInstance* stack_overflow_;
   RawInstance* out_of_memory_;
   RawObject** to() { return reinterpret_cast<RawObject**>(&out_of_memory_); }
 
   bool preallocate_objects_called_;
 
   friend class SnapshotReader;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectStore);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_STORE_H_