This change does IWYU additions for all cases where `base::DoNothing` is used. Furthermore, this change removes some of the uses of `base::DoNothing` as an argument default value in a header, removing the need to add `callback_helpers.h` to those headers. Chromium changes: https://chromium.googlesource.com/chromium/src/+/e8436cccafc34d6e4d9c060f682345060579d208 https://chromium.googlesource.com/chromium/src/+/227f058d9b9e27370a64b34046d71b9f23106409 commit e8436cccafc34d6e4d9c060f682345060579d208 Author: Lei Zhang <thestig@chromium.org> Date: Fri Dec 12 15:16:22 2025 -0800 Forward declare base::ScopedClosureRunner in some Blink headers Avoid including base/functional/callback_helpers.h when not needed. Also use base/functional/callback_forward.h since callback_helpers.h was providing callback.h. For scrollable_area.h, make this possible by getting rid the default arguments to PerformSnapping(), SnapAtCurrentPosition(), and SnapForEndPosition(). These methods have very few callers, so just pass in all the arguments. Then do IWYU to fix the build. Change-Id: I5cfd017bd6f392b0d97e99c41d4885fac7140a4c Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7254408 Commit-Queue: Philip Rogers <pdr@chromium.org> Auto-Submit: Lei Zhang <thestig@chromium.org> Reviewed-by: Philip Rogers <pdr@chromium.org> Reviewed-by: Christoph Schwering <schwering@google.com> Reviewed-by: Robert Flack <flackr@chromium.org> Cr-Commit-Position: refs/heads/main@{#1558318} commit 227f058d9b9e27370a64b34046d71b9f23106409 Author: Lei Zhang <thestig@chromium.org> Date: Thu Dec 11 21:30:12 2025 -0800 Do IWYU for callback_helpers.h in async_dom_storage_database.cc Add callback_helpers.h for base::DoNothing() usage. The transitive include that makes this work as-is will be deleted in the near future. Change-Id: Id5ba6db705434734a854874923b7bb196392ca6c Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7253640 Commit-Queue: Mingyu Lei <leimy@chromium.org> Auto-Submit: Lei Zhang <thestig@chromium.org> Reviewed-by: Mingyu Lei <leimy@chromium.org> Cr-Commit-Position: refs/heads/main@{#1557849}