Refactor isolate interrupts to use OOB messages instead of interrupt bits.

runtime/vm/service_isolate.cc

 // Copyright (c) 2015, 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/service_isolate.h"
 
 #include "vm/compiler.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/isolate.h"
@@ skipping 671 matching lines @@
     {
       // Print the error if there is one.  This may execute dart code to
       // print the exception object, so we need to use a StartIsolateScope.
       StartIsolateScope start_scope(I);
       Thread* T = Thread::Current();
       ASSERT(I == T->isolate());
       StackZone zone(T);
       HandleScope handle_scope(T);
       Error& error = Error::Handle(Z);
       error = I->object_store()->sticky_error();
-      if (!error.IsNull()) {
+      if (!error.IsNull() && !error.IsUnwindError()) {
         OS::PrintErr("vm-service: Error: %s\n", error.ToErrorCString());
       }
       Dart::RunShutdownCallback();
     }
     {
       // Shut the isolate down.
       SwitchIsolateScope switch_scope(I);
       Dart::ShutdownIsolate();
     }
     if (FLAG_trace_service) {
@@ skipping 144 matching lines @@
     return result;
   }
   Dart_Handle source = GetSource(url_string);
   if (Dart_IsError(source)) {
     return source;
   }
   return Dart_LoadSource(library, url, source, 0, 0);
 }
 
 }  // namespace dart