Re-add the discard reason to chrome://discards

This has been accidentally removed in
https://chromium-review.googlesource.com/c/chromium/src/+/1994427/10/chrome/browser/ui/webui/discards/discards_ui.cc#b215

Change-Id: Id5de050d8c1fa84ce0137abd87c1650b35aef084
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2036190Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Auto-Submit: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737901}

chrome/browser/ui/webui/discards/discards_ui.cc

@@ -202,6 +202,7 @@ class DiscardsDetailsProviderImpl : public discards::mojom::DetailsProvider {
       info->cannot_freeze_reasons = freeze_details.GetFailureReasonStrings();
       resource_coordinator::DecisionDetails discard_details;
       info->cannot_discard_reasons = discard_details.GetFailureReasonStrings();
+      info->discard_reason = lifecycle_unit->GetDiscardReason();
       info->discard_count = lifecycle_unit->GetDiscardCount();
       info->utility_rank = rank++;
       const base::TimeTicks last_focused_time =