Support generic synchronization against an IPC::Channel

ipc/ipc_channel_mojo.cc

Index: ipc/ipc_channel_mojo.cc
diff --git a/ipc/ipc_channel_mojo.cc b/ipc/ipc_channel_mojo.cc
index 0f12dd8cf0dfa0bf7de668cbc975e50cef79b9ba..ecc909d1ff9d0ca6909331b62898790d117bfccf 100644
--- a/ipc/ipc_channel_mojo.cc
+++ b/ipc/ipc_channel_mojo.cc
@@ -391,6 +391,11 @@ base::ProcessId ChannelMojo::GetSelfPID() const {
 Channel::AssociatedInterfaceSupport*
 ChannelMojo::GetAssociatedInterfaceSupport() { return this; }
 
+void ChannelMojo::SendEventToSignal(mojo::common::mojom::EventPtr event) {
+  if (message_reader_)
+    message_reader_->SendEventToSignal(std::move(event));
+}
+
 void ChannelMojo::OnPeerPidReceived() {
   listener_->OnChannelConnected(static_cast<int32_t>(GetPeerPID()));
 }