sync: Re-implement getAllNodes WebUI function

chrome/browser/sync/glue/sync_backend_host.h

Index: chrome/browser/sync/glue/sync_backend_host.h
diff --git a/chrome/browser/sync/glue/sync_backend_host.h b/chrome/browser/sync/glue/sync_backend_host.h
index caea2d08e4b9bb3102982f33b3b3ff10c013d7b0..1d1e3a03ba2aec226d592d7c1589528485d14a1f 100644
--- a/chrome/browser/sync/glue/sync_backend_host.h
+++ b/chrome/browser/sync/glue/sync_backend_host.h
@@ -201,6 +201,13 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
   // Disables protocol event forwarding.
   virtual void DisableProtocolEventForwarding() = 0;
 
+  // Returns a ListValue representing all nodes for the specified types through
+  // |callback| on this thread.
+  virtual void GetAllNodesForTypes(
+      syncer::ModelTypeSet types,
+      base::Callback<void(const std::vector<syncer::ModelType>&,
+                          ScopedVector<base::ListValue>)> type) = 0;
+
   virtual base::MessageLoop* GetSyncLoopForTesting() = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);