[Offline Pages] Moves Coordinator to using MarkAttemptStarted/MarkAttemptCompleted API.

components/offline_pages/background/save_page_request.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/background/save_page_request.h"
 
 namespace offline_pages {
 
 SavePageRequest::SavePageRequest(int64_t request_id,
                                  const GURL& url,
@@ skipping 60 matching lines @@
   // check here to ensure we only start tasks in status pending, and bail out in
   // other cases.
   last_attempt_time_ = start_time;
   ++attempt_count_;
 }
 
 void SavePageRequest::MarkAttemptCompleted() {
   last_attempt_time_ = base::Time();
 }
 
+void SavePageRequest::MarkAttemptAborted() {
+  DCHECK_GT(attempt_count_, 0);
+  last_attempt_time_ = base::Time();
+  // TODO(dougarnett): Would be safer if we had two persisted counters
+  // (attempts_started and attempts_completed) rather just one with decrement.
+  --attempt_count_;
+}
+
 }  // namespace offline_pages