Make UnixEventPort accessible through AsyncIoContext.

c++/src/kj/async-io.c++

@@ -792,6 +792,8 @@ public:
 
   Timer& getTimer() override { return timer; }
 
+  UnixEventPort& getEventPort() { return eventPort; }
+
 private:
   UnixEventPort eventPort;
   EventLoop eventLoop;
@@ -987,7 +989,7 @@ AsyncIoContext setupAsyncIo() {
   auto lowLevel = heap<LowLevelAsyncIoProviderImpl>();
   auto ioProvider = kj::heap<AsyncIoProviderImpl>(*lowLevel);
   auto& waitScope = lowLevel->getWaitScope();
-  return { kj::mv(lowLevel), kj::mv(ioProvider), waitScope };
+  return { kj::mv(lowLevel), kj::mv(ioProvider), waitScope, lowLevel->getEventPort() };
 }
 
 }  // namespace kj

c++/src/kj/async-io.h

@@ -31,6 +31,8 @@
 
 namespace kj {
 
+class UnixEventPort;
+
 class AsyncInputStream {
   // Asynchronous equivalent of InputStream (from io.h).
 
@@ -296,6 +298,10 @@ struct AsyncIoContext {
   Own<LowLevelAsyncIoProvider> lowLevelProvider;
   Own<AsyncIoProvider> provider;
   WaitScope& waitScope;
+
+  UnixEventPort& unixEventPort;
+  // TEMPORARY: Direct access to underlying UnixEventPort, mainly for waiting on signals. This
+  //   field will go away at some point when we have a chance to improve these interfaces.
 };
 
 AsyncIoContext setupAsyncIo();