Decrease the started_attempt_count_ for paused offlining requests.

This is a fix for the bug where 5 user pauses of an offlining request
fails the request because there is a max of 5 tries per request.
Decreasing the started_attempt_count_ when pausing an offlining request
undos the incrementation of the counter when the request began
offlining.

Bug: 701037
Change-Id: I721b41bd9e9a1c366c9fe7f5896f5627e8d8fb1a
Reviewed-on: https://chromium-review.googlesource.com/957423
Commit-Queue: Candice Sy <cmsy@google.com>
Reviewed-by: Yafei Duan <romax@chromium.org>
Reviewed-by: Peter Williamson <petewil@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543879}

components/offline_pages/core/background/change_requests_state_task.cc

@@ -44,6 +44,12 @@ void ChangeRequestsStateTask::UpdateRequests(
   // of the missing items will be added at the end.
   std::vector<SavePageRequest> items_to_update;
   for (auto request : read_result->updated_items) {
+    // Decrease the started_attempt_count_ for offlining requests paused by the
+    // user (https://crbug.com/701037).
+    if (request.request_state() == SavePageRequest::RequestState::OFFLINING &&
+        new_state_ == SavePageRequest::RequestState::PAUSED) {
+      request.set_started_attempt_count(request.started_attempt_count() - 1);
+    }
     request.set_request_state(new_state_);
     items_to_update.push_back(request);
   }

components/offline_pages/core/background/save_page_request.cc

@@ -59,12 +59,13 @@ void SavePageRequest::MarkAttemptCompleted() {
 }
 
 void SavePageRequest::MarkAttemptAborted() {
-  DCHECK_GT(started_attempt_count_, 0);
   // We intentinally do not increment the completed_attempt_count_, since this
   // was killed before it completed, so we could use the phone or browser for
   // other things.
-  if (state_ == RequestState::OFFLINING)
+  if (state_ == RequestState::OFFLINING) {
+    DCHECK_GT(started_attempt_count_, 0);
     state_ = RequestState::AVAILABLE;
+  }
 }
 
 void SavePageRequest::MarkAttemptPaused() {