Improve syncing between dom distiller and the print preview request

components/dom_distiller/core/dom_distiller_service.cc

Index: components/dom_distiller/core/dom_distiller_service.cc
diff --git a/components/dom_distiller/core/dom_distiller_service.cc b/components/dom_distiller/core/dom_distiller_service.cc
index 47d4f06d62986afcde2b3d376989f3a1380f3fc8..eeb177ef548705ddcbd1250110af944b5dc244ea 100644
--- a/components/dom_distiller/core/dom_distiller_service.cc
+++ b/components/dom_distiller/core/dom_distiller_service.cc
@@ -189,6 +189,16 @@ scoped_ptr<ViewerHandle> DomDistillerService::ViewUrl(
   return viewer_handle;
 }
 
+scoped_ptr<ViewerHandle> DomDistillerService::AddViewRequestDelegate(
+    ViewRequestDelegate* delegate,
+    const GURL& url) {
+  TaskTracker* task_tracker = GetTaskTrackerForUrl(url);
+  if (task_tracker)
+    return task_tracker->AddViewer(delegate);
+
+  return nullptr;
+}
+
 bool DomDistillerService::GetOrCreateTaskTrackerForUrl(
     const GURL& url,
     TaskTracker** task_tracker) {