Update mojo sdk to rev 7214b7ec7d27563b2666afad86cf1c5895c56c18

third_party/mojo/src/mojo/public/go/bindings/stub.go

Index: third_party/mojo/src/mojo/public/go/bindings/stub.go
diff --git a/third_party/mojo/src/mojo/public/go/bindings/stub.go b/third_party/mojo/src/mojo/public/go/bindings/stub.go
index b2b3120a08c0fe68c979b9657d4e95b399f9a755..c7ca09f51e6d757fb8fec4bf87369cdd51753d2e 100644
--- a/third_party/mojo/src/mojo/public/go/bindings/stub.go
+++ b/third_party/mojo/src/mojo/public/go/bindings/stub.go
@@ -4,6 +4,10 @@
 
 package bindings
 
+import (
+	"sync"
+)
+
 // MessageReceiver can receive |Message| objects.
 type MessageReceiver interface {
 	// Accept receives a |Message|. Returns a error if the message was not
@@ -16,6 +20,8 @@ type MessageReceiver interface {
 // implementation. If the method returns result, the stub serializes the
 // response and sends it back.
 type Stub struct {
+	// Makes sure that connector is closed only once.
+	closeOnce sync.Once
 	connector *Connector
 	receiver  MessageReceiver
 }
@@ -23,19 +29,27 @@ type Stub struct {
 // NewStub returns a new Stub instance using provided |Connector| to send and
 // receive messages. Incoming messages are handled by the provided |receiver|.
 func NewStub(connector *Connector, receiver MessageReceiver) *Stub {
-	return &Stub{connector, receiver}
+	return &Stub{
+		connector: connector,
+		receiver:  receiver,
+	}
 }
 
 // ServeRequest synchronously serves one request from the message pipe: the
 // |Stub| waits on its underlying message pipe for a message and handles it.
 // Can be called from multiple goroutines. Each calling goroutine will receive
-// a different message or an error.
+// a different message or an error. Closes itself in case of error.
 func (s *Stub) ServeRequest() error {
 	message, err := s.connector.ReadMessage()
 	if err != nil {
+		s.Close()
 		return err
 	}
-	return s.receiver.Accept(message)
+	err = s.receiver.Accept(message)
+	if err != nil {
+		s.Close()
+	}
+	return err
 }
 
 // Close immediately closes the |Stub| and its underlying message pipe. If the
@@ -43,5 +57,7 @@ func (s *Stub) ServeRequest() error {
 // All goroutines trying to serve will start returning errors as the underlying
 // message pipe becomes invalid.
 func (s *Stub) Close() {
-	s.connector.Close()
+	s.closeOnce.Do(func() {
+		s.connector.Close()
+	})
 }