Mojo: Don't do any work in ProxyMessagePipeEndpoint's destructor.

mojo/system/proxy_message_pipe_endpoint.cc

Index: mojo/system/proxy_message_pipe_endpoint.cc
diff --git a/mojo/system/proxy_message_pipe_endpoint.cc b/mojo/system/proxy_message_pipe_endpoint.cc
index a14fa965b136a6e6ae68a2a1bc4e1b3cc6f02f5a..935955caaacd0062c4016abd2b4c03bc0036259c 100644
--- a/mojo/system/proxy_message_pipe_endpoint.cc
+++ b/mojo/system/proxy_message_pipe_endpoint.cc
@@ -20,7 +20,7 @@ ProxyMessagePipeEndpoint::ProxyMessagePipeEndpoint(
 }
 
 ProxyMessagePipeEndpoint::~ProxyMessagePipeEndpoint() {
-  channel_endpoint_->DetachFromMessagePipe();
+  DCHECK(!channel_endpoint_.get());
 }
 
 MessagePipeEndpoint::Type ProxyMessagePipeEndpoint::GetType() const {
@@ -28,6 +28,7 @@ MessagePipeEndpoint::Type ProxyMessagePipeEndpoint::GetType() const {
 }
 
 bool ProxyMessagePipeEndpoint::OnPeerClose() {
+  DetachIfNecessary();
   return false;
 }
 
@@ -41,5 +42,16 @@ void ProxyMessagePipeEndpoint::EnqueueMessage(
       << "Failed to write enqueue message to channel";
 }
 
+void ProxyMessagePipeEndpoint::Close() {
+  DetachIfNecessary();
+}
+
+void ProxyMessagePipeEndpoint::DetachIfNecessary() {
+  if (channel_endpoint_.get()) {
+    channel_endpoint_->DetachFromMessagePipe();
+    channel_endpoint_ = nullptr;
+  }
+}
+
 }  // namespace system
 }  // namespace mojo