[mojo-edk] Prevent watching an invalid FD on early broker pipe closure

mojo/edk/system/node_controller.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/system/node_controller.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 184 matching lines @@
 void NodeController::ConnectToParent(ScopedPlatformHandle platform_handle) {
 // TODO(amistry): Consider the need for a broker on Windows.
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_NACL)
   // On posix, use the bootstrap channel for the broker and receive the node's
   // channel synchronously as the first message from the broker.
   base::ElapsedTimer timer;
   broker_.reset(new Broker(std::move(platform_handle)));
   platform_handle = broker_->GetParentPlatformHandle();
   UMA_HISTOGRAM_TIMES("Mojo.System.GetParentPlatformHandleSyncTime",
                       timer.Elapsed());
+
+  if (!platform_handle.is_valid()) {
+    // Most likely the browser side of the channel has already been closed and
+    // the broker was unable to negotiate a NodeChannel pipe. In this case we
+    // can cancel parent connection.
+    DVLOG(1) << "Cannot connect to invalid parent channel.";
+    return;
+  }
 #endif
 
   io_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&NodeController::ConnectToParentOnIOThread,
                  base::Unretained(this),
                  base::Passed(&platform_handle)));
 }
 
 void NodeController::SetPortObserver(
@@ skipping 913 matching lines @@
     shutdown_callback_flag_.Set(false);
   }
 
   DCHECK(!callback.is_null());
 
   callback.Run();
 }
 
 }  // namespace edk
 }  // namespace mojo