sync: Support nudges from non-blocking sync types

sync/engine/nudge_handler.cc

Index: sync/engine/nudge_handler.cc
diff --git a/sync/engine/update_handler.cc b/sync/engine/nudge_handler.cc
similarity index 65%
copy from sync/engine/update_handler.cc
copy to sync/engine/nudge_handler.cc
index 308fee95bb1074c197b6973f38b49eb017d9ba7c..9c0ef7dd8400b8986ed135441a4d8dd75ed0df08 100644
--- a/sync/engine/update_handler.cc
+++ b/sync/engine/nudge_handler.cc
@@ -2,13 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "sync/engine/update_handler.h"
+#include "sync/engine/nudge_handler.h"
 
 namespace syncer {
 
-UpdateHandler::UpdateHandler() {}
-
-UpdateHandler::~UpdateHandler() {}
+NudgeHandler::NudgeHandler() {

[stanisc, 2014/07/09 22:35:24]

Since NudgeHandler is effectively an interface, why aren't these trivial
constructor and destructor inlined in the header file? 

[rlarocque, 2014/07/10 00:12:29]

I've seen the windows trybots sometimes fail to link when SYNC_EXPORT'ed
functions are declared in the header file.  Moving them to the .cc file fixes
it, so I've started declaring even trivial functions int he .cc file as a
precaution.

Besides, I see no harm in moving these functions to the .cc file.

+}
 
+NudgeHandler::~NudgeHandler() {
+}
 
 }  // namespace syncer