[Background Fetch] Fix UpdateUI icon update.

The JobDetails were being deleted before the OIC could query for the updated visuals.
The breaking change was not merged into M71.

Change-Id: I8dcbaa5916001198006a3550c3bfc337436d62cf
Reviewed-on: https://chromium-review.googlesource.com/c/1333807Reviewed-by: Peter Beverloo <peter@chromium.org>
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607961}

chrome/browser/background_fetch/background_fetch_delegate_impl.cc

@@ -340,10 +340,6 @@ void BackgroundFetchDelegateImpl::UpdateUI(
   }
 
   UpdateOfflineItemAndUpdateObservers(&job_details);
-
-  // UpdateUI() can only be called once, and only when the background fetch
-  // has succeeded or failed, so we can delete |job_details| now.
-  job_details_map_.erase(job_details_iter);
 }
 
 void BackgroundFetchDelegateImpl::OnDownloadStarted(