Fix a number of issues with the process handling

runtime/bin/eventhandler_macos.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 <errno.h>
 #include <poll.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/time.h>
@@ skipping 248 matching lines @@
           if (bytesPeeked == 0) {
             event_mask = (1 << kCloseEvent);
             sd->MarkClosedRead();
           } else if (errno != EAGAIN) {
             fprintf(stderr, "Error recv: %s\n", strerror(errno));
           }
         }
       }
     }
 
-    // On pipes POLLHUP is reported without POLLIN.
+    // On pipes POLLHUP is reported without POLLIN when there is no
+    // more data to read.
     if (sd->IsPipe()) {
       if (((pollfd->revents & POLLIN) == 0) &&
           ((pollfd->revents & POLLHUP) != 0)) {
         event_mask = (1 << kCloseEvent);
         sd->MarkClosedRead();
       }
     }
 
-    if ((pollfd->revents & POLLOUT) != 0) event_mask |= (1 << kOutEvent);
+    if ((pollfd->revents & POLLOUT) != 0) {
+      if ((pollfd->revents & POLLERR) != 0) {
+        event_mask = (1 << kErrorEvent);
+        sd->MarkClosedWrite();
+      } else {
+        event_mask |= (1 << kOutEvent);
+      }
+    }
   }
 
   return event_mask;
 }
 
 
 void EventHandlerImplementation::HandleEvents(struct pollfd* pollfds,
                                               int pollfds_size,
                                               int result_size) {
   if ((pollfds[0].revents & POLLIN) != 0) {
@@ skipping 72 matching lines @@
     FATAL("Create start event handler thread");
   }
 }
 
 
 void EventHandlerImplementation::SendData(intptr_t id,
                                           Dart_Port dart_port,
                                           intptr_t data) {
   WakeupHandler(id, dart_port, data);
 }