If an unhandled exception occurs in Dart_RunLoop, pass it out to the caller.

runtime/vm/dart_entry.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_DART_ENTRY_H_
 #define VM_DART_ENTRY_H_
 
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
 
 namespace dart {
 
 // Forward declarations.
 class Array;
 class Closure;
 class Context;
 class Function;
 class Instance;
 class Integer;
 class Object;
 class RawInstance;
 class String;
 
 // DartEntry abstracts functionality needed to resolve dart functions
 // and invoke them from C++.
+//
+// TODO(turnidge): Make these functions assert that there is an active
+// setjmp.  Or make these functions do the setjmps themselves and
+// represent compile errors with an explict object type.
+//
+// TODO(turnidge): Make these functions return RawObject instead of
+// RawInstance.
 class DartEntry : public AllStatic {
  public:
   typedef RawInstance* (*invokestub)(uword entry_point,
                                      const Array& arguments_descriptor,
                                      const Object** arguments,
                                      const Context& context);
 
   // Invoke the specified instance function on the receiver.
   // Returns object returned by the dart instance function.
   static RawInstance* InvokeDynamic(
@@ skipping 20 matching lines @@
 
 // Utility functions to call from VM into Dart bootstrap libraries.
 // Each may return an exception object.
 class DartLibraryCalls : public AllStatic {
  public:
   static RawInstance* ExceptionCreate(
       const String& exception_name,
       const GrowableArray<const Object*>& arguments);
   static RawInstance* ToString(const Instance& receiver);
   static RawInstance* Equals(const Instance& left, const Instance& right);
+
+  // Returns either an unhandled exception or null.
+  static RawObject* HandleMessage(Dart_Port dest_port_id,
+                                  Dart_Port reply_port_id,
+                                  const Instance& dart_message);
 };
 
 }  // namespace dart
 
 #endif  // VM_DART_ENTRY_H_