Use VM type cast and save handles.

runtime/vm/exceptions.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_EXCEPTIONS_H_
 #define VM_EXCEPTIONS_H_
 
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
 
@@ skipping 10 matching lines @@
 class RawObject;
 class Script;
 class String;
 
 class Exceptions : AllStatic {
  public:
   static const char* kCastExceptionDstName;
 
   static void Throw(const Instance& exception);
   static void ReThrow(const Instance& exception, const Instance& stacktrace);
-  static void PropagateError(const Object& obj);
+  static void PropagateError(const Error& error);
 
   // Helpers to create and throw errors.
   static RawScript* GetCallerScript(DartFrameIterator* iterator);
   static RawInstance* NewInstance(const char* class_name);
   static void SetField(const Instance& instance,
                        const Class& cls,
                        const char* field_name,
                        const Object& value);
   static void SetLocationFields(const Instance& instance,
                                 const Class& cls,
@@ skipping 28 matching lines @@
   static RawObject* Create(ExceptionType type,
                            const GrowableArray<const Object*>& arguments);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Exceptions);
 };
 
 }  // namespace dart
 
 #endif  // VM_EXCEPTIONS_H_