[offline page mode] Initialize bool

Class OfflinePageModel:SavePageParams was using an unset bool.
It's now initialized in the constructor.

Change-Id: Ie810decf6eb27c5ca0be020b52d5df3f4c43a7c8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1699090Reviewed-by: Jian Li <jianli@chromium.org>
Commit-Queue: Kevin Bailey <krb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#677066}

components/offline_pages/core/offline_page_model.cc

@@ -12,7 +12,8 @@ const int64_t OfflinePageModel::kInvalidOfflineId;
 
 OfflinePageModel::SavePageParams::SavePageParams()
     : proposed_offline_id(OfflinePageModel::kInvalidOfflineId),
-      is_background(false) {}
+      is_background(false),
+      use_page_problem_detectors(false) {}
 
 OfflinePageModel::SavePageParams::SavePageParams(const SavePageParams& other) =
     default;