Implement reset_on_disconnect() on AssociatedReceiver

I'm using AssociatedReceivers in the //remoting directory for our IPC
and wanted a way to reset the receiver automatically when the process
on the other side of the connection crashes. This is the same method
I recently added to AssociatedRemote however the associate remote
and receiver impls don't share a base class so I put it in the
AssociatedReceiverBase header.

Bug: NO_BUG
Change-Id: Ie40101145e5a6446f9623803fdc93e05470bd97a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3268785
Reviewed-by: Yuwei Huang <yuweih@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Commit-Queue: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#939936}

mojo/public/cpp/bindings/associated_receiver.h

@@ -39,6 +39,7 @@ class COMPONENT_EXPORT(MOJO_CPP_BINDINGS) AssociatedReceiverBase {
   void set_disconnect_handler(base::OnceClosure error_handler);
   void set_disconnect_with_reason_handler(
       ConnectionErrorWithReasonCallback error_handler);
+  void reset_on_disconnect();
 
   bool is_bound() const { return !!endpoint_client_; }
   explicit operator bool() const { return !!endpoint_client_; }
@@ -149,6 +150,12 @@ class AssociatedReceiver : public internal::AssociatedReceiverBase {
   // about why the remote endpoint was closed, if provided.
   using AssociatedReceiverBase::set_disconnect_with_reason_handler;
 
+  // Resets this AssociatedReceiver on disconnect. Note that this replaces any
+  // previously set disconnection handler. Must be called on a bound
+  // AssociatedReceiver object, and only remains set as long as the
+  // AssociatedReceiver is both bound and connected.
+  using AssociatedReceiverBase::reset_on_disconnect;
+
   // Resets this AssociatedReceiver to an unbound state. An unbound
   // AssociatedReceiver will NEVER schedule method calls or disconnection
   // notifications, and any pending tasks which were scheduled prior to

mojo/public/cpp/bindings/lib/associated_receiver.cc

@@ -46,6 +46,12 @@ void AssociatedReceiverBase::set_disconnect_with_reason_handler(
       std::move(error_handler));
 }
 
+void AssociatedReceiverBase::reset_on_disconnect() {
+  DCHECK(is_bound());
+  set_disconnect_handler(
+      base::BindOnce(&AssociatedReceiverBase::reset, base::Unretained(this)));
+}
+
 void AssociatedReceiverBase::FlushForTesting() {
   endpoint_client_->FlushForTesting();  // IN-TEST
 }

remoting/host/desktop_session_win.cc

@@ -747,13 +747,9 @@ void DesktopSessionWin::OnAssociatedInterfaceRequest(
         pending_receiver(std::move(handle));
     desktop_session_request_handler_.Bind(std::move(pending_receiver));
 
-    // Set up a disconnect handler so |desktop_session_request_handler_| can be
-    // re-bound if |launcher_| spawns a new desktop process.
-    // TODO(joedow): Add a reset_on_disconnect() method on associated receiver.
-    desktop_session_request_handler_.set_disconnect_handler(base::BindOnce(
-        [](mojo::AssociatedReceiver<mojom::DesktopSessionRequestHandler>*
-               receiver) { receiver->reset(); },
-        base::Unretained(&desktop_session_request_handler_)));
+    // Reset the receiver on disconnect so |desktop_session_request_handler_|
+    // can be re-bound if |launcher_| spawns a new desktop process.
+    desktop_session_request_handler_.reset_on_disconnect();
   } else {
     LOG(ERROR) << "Unknown associated interface requested: " << interface_name
                << ", crashing the desktop process";