Have the RequestCoordinator generate the offline_id

components/offline_pages/offline_page_model_impl.cc

 // Copyright 2016 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/offline_pages/offline_page_model_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 257 matching lines @@
   observers_.AddObserver(observer);
 }
 
 void OfflinePageModelImpl::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
 void OfflinePageModelImpl::SavePage(
     const GURL& url,
     const ClientId& client_id,
+    int64_t proposed_offline_id,
     std::unique_ptr<OfflinePageArchiver> archiver,
     const SavePageCallback& callback) {
   DCHECK(is_loaded_);
 
   // Skip saving the page that is not intended to be saved, like local file
   // page.
   if (!OfflinePageModel::CanSaveURL(url)) {
     InformSavePageDone(callback, SavePageResult::SKIPPED, client_id,
                        kInvalidOfflineId);
     return;
   }
 
   // The web contents is not available if archiver is not created and passed.
   if (!archiver.get()) {
     InformSavePageDone(callback, SavePageResult::CONTENT_UNAVAILABLE, client_id,
                        kInvalidOfflineId);
     return;
   }
 
-  int64_t offline_id = GenerateOfflineId();
+  // If we already have an offline id, use it.  If not, generate one.
+  if (proposed_offline_id == 0ul)

[dougarnett, 2016/08/18 17:59:07]

negative proposed ids ok?

+    proposed_offline_id = GenerateOfflineId();
 
   archiver->CreateArchive(
-      archives_dir_, offline_id,
+      archives_dir_, proposed_offline_id,
       base::Bind(&OfflinePageModelImpl::OnCreateArchiveDone,
-                 weak_ptr_factory_.GetWeakPtr(), url, offline_id, client_id,
-                 base::Time::Now(), callback));
+                 weak_ptr_factory_.GetWeakPtr(), url, proposed_offline_id,
+                 client_id, base::Time::Now(), callback));
   pending_archivers_.push_back(std::move(archiver));
 }
 
 void OfflinePageModelImpl::MarkPageAccessed(int64_t offline_id) {
   RunWhenLoaded(base::Bind(&OfflinePageModelImpl::MarkPageAccessedWhenLoadDone,
                            weak_ptr_factory_.GetWeakPtr(), offline_id));
 }
 
 void OfflinePageModelImpl::MarkPageAccessedWhenLoadDone(int64_t offline_id) {
   DCHECK(is_loaded_);
@@ skipping 746 matching lines @@
 void OfflinePageModelImpl::RunWhenLoaded(const base::Closure& task) {
   if (!is_loaded_) {
     delayed_tasks_.push_back(task);
     return;
   }
 
   base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE, task);
 }
 
 }  // namespace offline_pages