[iOS] Remove experimental Discover feed background refresh.

This CL removes all of the code, and most of the flags, used to control
the background refresh experiment for the Discover feed implemented in
DiscoverFeedAppAgent.

The app agent itself still implements a related but wholly distinct
feature where the feed is updated when Chrome *enters* the background.

The flag IsFeedBackgroundRefreshEnabled() is retained for future use
when feed refresh is implemented in the new background refresh
architecture. There's no longer storage of the flag value in defaults;
depending on the final implementation of background feed refresh using
the new infrastructure, this may need to be added back.

Bug: 349339414
Change-Id: I62fd8297be34e7db112a1073306dfedf255ee4aa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6244017
Commit-Queue: Mark Cogan <marq@chromium.org>
Reviewed-by: Adam Arcaro <adamta@google.com>
Cr-Commit-Position: refs/heads/main@{#1417344}
NOKEYCHECK=True
GitOrigin-RevId: 396f652ee7a6dbf0ef5cc74077093dd0110b5f8f
6 files changed
tree: 40b1219f64ce7a29c5a3c7697334be9b280d1755
  1. build/
  2. chrome/
  3. components/
  4. google_internal/
  5. intents/
  6. net/
  7. public/
  8. testing/
  9. third_party/
  10. tools/
  11. web/
  12. web_view/
  13. .swift-format
  14. BUILD.gn
  15. COMMON_METADATA
  16. DEPS
  17. DIR_METADATA
  18. features.gni
  19. OWNERS
  20. PRESUBMIT.py
  21. PRESUBMIT_test.py
  22. README.md
README.md

This directory holds code related to Chrome for iOS. See this document for a description of the structure underneath this directory.