Support generic synchronization against an IPC::Channel

ipc/ipc_channel_proxy.cc

Index: ipc/ipc_channel_proxy.cc
diff --git a/ipc/ipc_channel_proxy.cc b/ipc/ipc_channel_proxy.cc
index f99274f1555f422e13138a3c6ca4648cec434fd5..8a7bdaa6ccdbc91f256f78f4de9552f6d41fbb58 100644
--- a/ipc/ipc_channel_proxy.cc
+++ b/ipc/ipc_channel_proxy.cc
@@ -429,6 +429,13 @@ void ChannelProxy::Context::GetRemoteAssociatedInterface(
       name, std::move(handle));
 }
 
+// Called on the IPC::Channel thread
+void ChannelProxy::Context::SendEventToSignal(
+    mojo::common::mojom::EventPtr event) {
+  if (channel_)
+    channel_->SendEventToSignal(std::move(event));
+}
+
 //-----------------------------------------------------------------------------
 
 // static
@@ -584,6 +591,15 @@ void ChannelProxy::RemoveFilter(MessageFilter* filter) {
                             base::RetainedRef(filter)));
 }
 
+mojo::common::mojom::EventRequest ChannelProxy::CreateSynchronizationEvent() {
+  mojo::common::mojom::EventPtr event;
+  mojo::common::mojom::EventRequest request = mojo::GetProxy(&event);
+  context_->ipc_task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(&Context::SendEventToSignal, context_, base::Passed(&event)));
+  return request;
+}
+
 void ChannelProxy::AddGenericAssociatedInterface(
     const std::string& name,
     const GenericAssociatedInterfaceFactory& factory) {