Ensure that the ThreadInterrupter is awake after debugging

runtime/vm/message_handler.cc

Index: runtime/vm/message_handler.cc
diff --git a/runtime/vm/message_handler.cc b/runtime/vm/message_handler.cc
index 34e3b40a2900d290dcd2011bd69f983b05865d9e..6a473dd74033f4c6d019be2437de0c7a8ec29aa9 100644
--- a/runtime/vm/message_handler.cc
+++ b/runtime/vm/message_handler.cc
@@ -7,6 +7,7 @@
 #include "vm/dart.h"
 #include "vm/lockers.h"
 #include "vm/port.h"
+#include "vm/thread_interrupter.h"
 
 namespace dart {
 
@@ -145,6 +146,10 @@ bool MessageHandler::HandleMessages(bool allow_normal_messages,
   // If isolate() returns NULL StartIsolateScope does nothing.
   StartIsolateScope start_isolate(isolate());
 
+  // ThreadInterrupter may have gone to sleep waiting while waiting for
+  // an isolate to start handling messages.
+  ThreadInterrupter::WakeUp();
+
   // TODO(turnidge): Add assert that monitor_ is held here.
   bool result = true;
   Message::Priority min_priority = (allow_normal_messages && !paused()) ?