Add embedder::AsyncWait()

mojo/edk/system/core.cc

Index: mojo/edk/system/core.cc
diff --git a/mojo/edk/system/core.cc b/mojo/edk/system/core.cc
index 3843d9714a7702c36e2290e382976eaf0c08388b..6189e5031d11c231537448348da03a37a5124ac2 100644
--- a/mojo/edk/system/core.cc
+++ b/mojo/edk/system/core.cc
@@ -10,6 +10,7 @@
 #include "base/time/time.h"
 #include "mojo/edk/embedder/platform_shared_buffer.h"
 #include "mojo/edk/embedder/platform_support.h"
+#include "mojo/edk/system/async_waiter.h"
 #include "mojo/edk/system/configuration.h"
 #include "mojo/edk/system/data_pipe.h"
 #include "mojo/edk/system/data_pipe_consumer_dispatcher.h"
@@ -97,6 +98,19 @@ scoped_refptr<Dispatcher> Core::GetDispatcher(MojoHandle handle) {
   return handle_table_.GetDispatcher(handle);
 }
 
+MojoResult Core::AsyncWait(MojoHandle handle,
+                           MojoHandleSignals signals,
+                           base::Callback<void(MojoResult)> callback) {
+  scoped_refptr<Dispatcher> dispatcher = GetDispatcher(handle);
+  DCHECK(dispatcher);
+
+  scoped_ptr<AsyncWaiter> waiter = make_scoped_ptr(new AsyncWaiter(callback));
+  MojoResult rv = dispatcher->AddAwakable(waiter.get(), signals, 0, nullptr);
+  if (rv == MOJO_RESULT_OK)
+    ignore_result(waiter.release());
+  return rv;
+}
+
 MojoTimeTicks Core::GetTimeTicksNow() {
   return base::TimeTicks::Now().ToInternalValue();
 }