Async: add sh_ptr<ContinuationChainLink> to Callback<>

This change enables us to finally implement the tracing of
continuations backward from the point of acquisition for deadlock
debugging.

senseApis/xcbWindow/xcbWindow.cpp

@@ -8,6 +8,7 @@
 #include <xcb/xcb.h>
 #include <user/senseApiDesc.h>
 #include <user/deviceAttachmentSpec.h>
+#include <callback.h>
 #include <xcbXorg/xcbXorg.h>
 #include "xcbWindow.h"
 
@@ -276,7 +277,7 @@ static int xcbWindow_finalizeInd(void)
 static void xcbWindow_attachDeviceReq(
     const std::shared_ptr<smo::device::DeviceAttachmentSpec>& desc,
     const std::shared_ptr<smo::ComponentThread>& componentThread,
-	smo::sense_api::sal_mlo_attachDeviceReqCbFn cb
+	smo::Callback<smo::sense_api::sal_mlo_attachDeviceReqCbFn> cb
     )
 {
 	// Not used yet, but may be used later.
@@ -289,12 +290,12 @@ static void xcbWindow_attachDeviceReq(
         << g_attachedWindows.back()->stringify()
         << "\n";
 
-    cb(true, desc);
+    cb.callbackFn(true, desc);
 }
 
 static void xcbWindow_detachDeviceReq(
     const std::shared_ptr<smo::device::DeviceAttachmentSpec>& spec,
-	smo::sense_api::sal_mlo_detachDeviceReqCbFn cb
+	smo::Callback<smo::sense_api::sal_mlo_detachDeviceReqCbFn> cb
     )
 {
     auto it = std::find_if(g_attachedWindows.begin(), g_attachedWindows.end(),
@@ -308,7 +309,7 @@ static void xcbWindow_detachDeviceReq(
 		std::cerr << __func__ << ": Device not found for detachment:\n"
 			<< spec->stringify() << "\n";
 
-		cb(false, spec);
+		cb.callbackFn(false, spec);
 		return;
     }
 
@@ -316,7 +317,7 @@ static void xcbWindow_detachDeviceReq(
     std::cout << __func__ << ": Detached X11 window device:\n"
         << spec->stringify() << "\n";
 
-	cb(true, spec);
+	cb.callbackFn(true, spec);
 }
 
 // SenseApi descriptor