If MHTML saving is cancelled, delete the page afterwards.

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/bind.h"
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sys_info.h"
@@ skipping 63 matching lines @@
                          "OfflinePages.Background.BackgroundLoadingFailedCode"),
       std::abs(error_code));
 }
 
 void HandleApplicationStateChangeCancel(
     const Offliner::CompletionCallback& completion_callback,
     const SavePageRequest& canceled_request) {
   completion_callback.Run(canceled_request,
                           Offliner::RequestStatus::FOREGROUND_CANCELED);
 }
+
+void LocalDeletePageCallback(DeletePageResult result) {}
 }  // namespace
 
 BackgroundLoaderOffliner::BackgroundLoaderOffliner(
     content::BrowserContext* browser_context,
     const OfflinerPolicy* policy,
     OfflinePageModel* offline_page_model)
     : browser_context_(browser_context),
       offline_page_model_(offline_page_model),
       policy_(policy),
       is_low_end_device_(base::SysInfo::IsLowEndDevice()),
@@ skipping 313 matching lines @@
 void BackgroundLoaderOffliner::OnPageSaved(SavePageResult save_result,
                                            int64_t offline_id) {
   if (!pending_request_)
     return;
 
   SavePageRequest request(*pending_request_.get());
   bool did_snapshot_on_last_retry = did_snapshot_on_last_retry_;
   ResetState();
 
   if (save_state_ == DELETE_AFTER_SAVE) {
+    // Delete the saved page off disk and from the OPM.
+    std::vector<int64_t> offline_ids;
+    offline_ids.push_back(offline_id);
+    offline_page_model_->DeletePagesByOfflineId(
+        offline_ids, base::Bind(&LocalDeletePageCallback));

[chili, 2017/04/29 00:11:33]

should we only run the cancel_callback_.Run once the delete completes?

Do we have to worry about a situation where the subsequent pending_request
starts to save before delete completes?

[Pete Williamson, 2017/04/29 00:14:44]

My thinking here is that it is fine to return control.  We only need to clean up
the page.  If we get another request for the same page, it will have a different
request ID, so the page being cleaned up should not interefere with the
operation.  If another request starts to save while deleting the page, they
should also be independent.

     save_state_ = NONE;
     cancel_callback_.Run(request);
     return;
   }
 
   save_state_ = NONE;
 
   Offliner::RequestStatus save_status;
   if (save_result == SavePageResult::ALREADY_EXISTS) {
     save_status = RequestStatus::SAVED;
@@ skipping 49 matching lines @@
   // Given the choice between int and double, we choose to implicitly convert to
   // a double since it maintains more precision (we can get a longer time in
   // milliseconds than we can with a 2 bit int, 53 bits vs 32).
   double delay = delay_so_far.InMilliseconds();
   signal_data_.SetDouble(signal_name, delay);
 }
 
 }  // namespace offline_pages
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(offline_pages::OfflinerData);