[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/dispatcher.cc

Index: mojo/edk/system/dispatcher.cc
diff --git a/mojo/edk/system/dispatcher.cc b/mojo/edk/system/dispatcher.cc
index d475ef6fa0da4bafbe49c5bd4de930f24544c419..bbc9c668b4e624e521305ef15a188e90ca3319d9 100644
--- a/mojo/edk/system/dispatcher.cc
+++ b/mojo/edk/system/dispatcher.cc
@@ -19,6 +19,16 @@ Dispatcher::DispatcherInTransit::DispatcherInTransit() {}
 
 Dispatcher::DispatcherInTransit::~DispatcherInTransit() {}
 
+MojoResult Dispatcher::Watch(MojoHandleSignals signals,
+                             const Watcher::WatchCallback& callback,
+                             uintptr_t context) {
+  return MOJO_RESULT_INVALID_ARGUMENT;
+}
+
+MojoResult Dispatcher::CancelWatch(uintptr_t context) {
+  return MOJO_RESULT_INVALID_ARGUMENT;
+}
+
 MojoResult Dispatcher::WriteMessage(const void* bytes,
                                     uint32_t num_bytes,
                                     const DispatcherInTransit* dispatchers,