Improve syncing between dom distiller and the print preview request

components/dom_distiller/core/dom_distiller_service.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/dom_distiller/core/dom_distiller_service.h"
 
 #include <utility>
 
 #include "base/guid.h"
 #include "base/location.h"
@@ skipping 171 matching lines @@
   // If a distiller is already running for one URL, don't start another.
   if (was_created) {
     task_tracker->StartDistiller(distiller_factory_.get(),
                                  std::move(distiller_page));
     task_tracker->StartBlobFetcher();
   }
 
   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) {
   ArticleEntry entry;
   if (store_->GetEntryByUrl(url, &entry)) {
     return GetOrCreateTaskTrackerForEntry(entry, task_tracker);
   }
 
   *task_tracker = GetTaskTrackerForUrl(url);
   if (*task_tracker) {
@@ skipping 74 matching lines @@
 void DomDistillerService::RemoveObserver(DomDistillerObserver* observer) {
   DCHECK(observer);
   store_->RemoveObserver(observer);
 }
 
 DistilledPagePrefs* DomDistillerService::GetDistilledPagePrefs() {
   return distilled_page_prefs_.get();
 }
 
 }  // namespace dom_distiller