Treat already existing saved pages as success.

chrome/browser/android/offline_pages/background_loader_offliner.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 "chrome/browser/android/offline_pages/background_loader_offliner.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "base/sys_info.h"
 #include "chrome/browser/android/offline_pages/offline_page_mhtml_archiver.h"
 #include "chrome/browser/android/offline_pages/offliner_helper.h"
@@ skipping 346 matching lines @@
 
   if (save_state_ == DELETE_AFTER_SAVE) {
     save_state_ = NONE;
     cancel_callback_.Run(request.request_id());
     return;
   }
 
   save_state_ = NONE;
 
   Offliner::RequestStatus save_status;
-  if (save_result == SavePageResult::SUCCESS) {
+  if (save_result == SavePageResult::SUCCESS ||
+      save_result == SavePageResult::ALREADY_EXISTS) {

[fgorski, 2017/04/24 19:51:51]

Hey, 3 questions:
1. Did you check if we maybe remove the file if we get already_exists.

2. Also if it already exists, why would you consider it "on last retry" below?

3. What about a corresponding change on Prerendering offliner side to keep the
expectation in line?

[Pete Williamson, 2017/04/25 00:09:00]

We don't remove it, because we then get the same error on the next try.
It's a bit ambiguous, but I changed the code to not count it as a last retry.
Done (but no unit test added).

     if (did_snapshot_on_last_retry)
       save_status = RequestStatus::SAVED_ON_LAST_RETRY;
     else
       save_status = RequestStatus::SAVED;
   } else {
     save_status = RequestStatus::SAVE_FAILED;
   }
 
   completion_callback_.Run(request, save_status);
 }
@@ skipping 37 matching lines @@
     int64_t offline_id) {
   // If for some reason the request was reset during while waiting for callback
   // ignore the completion callback.
   if (pending_request_ && pending_request_->request_id() != offline_id)
     return;
   completion_callback_.Run(request, RequestStatus::FOREGROUND_CANCELED);
 }
 }  // namespace offline_pages
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(offline_pages::OfflinerData);