Handle spurious wakeups properly.

runtime/vm/isolate.cc

 // 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.
 
 #include "vm/isolate.h"
 
 #include "include/dart_api.h"
 
 #include "vm/assert.h"
 #include "vm/bigint_store.h"
@@ skipping 224 matching lines @@
 void Isolate::StandardRunLoop() {
   ASSERT(long_jump_base() != NULL);
   ASSERT(post_message_callback() == &StandardPostMessageCallback);
   ASSERT(close_port_callback() == &StandardClosePortCallback);
 
   while (active_ports() > 0) {
     Zone zone;
     HandleScope handle_scope;
 
     PortMessage* message = message_queue()->Dequeue(0);
-    ASSERT(message != NULL);
-    Dart_HandleMessage(
-        message->dest_port(), message->reply_port(), message->data());
-    delete message;
+    if (message != NULL) {
+      Dart_HandleMessage(
+          message->dest_port(), message->reply_port(), message->data());
+      delete message;
+    }
   }
 }
 
 
 void Isolate::VisitObjectPointers(ObjectPointerVisitor* visitor,
                                   bool validate_frames) {
   ASSERT(visitor != NULL);
 
   // Visit objects in the object store.
   object_store()->VisitObjectPointers(visitor);
@@ skipping 20 matching lines @@
   // Visit all objects in the code index table.
   if (code_index_table() != NULL) {
     code_index_table()->VisitObjectPointers(visitor);
   }
 
   // Visit the top context which is stored in the isolate.
   visitor->VisitPointer(reinterpret_cast<RawObject**>(&top_context_));
 }
 
 }  // namespace dart