GitLab

- New field SelectFilesResult->picker_activity
- New enum value FileSelectorEventType::CLICK_CANCEL

SelectFilesResult and FileSelectorEventType are not used in released
clients yet, so it's safe to modify them

Design doc : go/arc-file-picker-get-content

BUG=b:130204519
TEST=unit_tests --gtest_filter="ArcSelectFilesHandlerTest.*"

Debug File Manager GET_CONTENT implementation

Change-Id: Id28bda1e1f96dc11072c34db9b4edcda9d14c50a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1580692
Commit-Queue: Satoshi Niwa <niwa@chromium.org>
Auto-Submit: Satoshi Niwa <niwa@chromium.org>
Reviewed-by: Ryo Hashimoto <hashimoto@chromium.org>
Reviewed-by: Greg Kerr <kerrnel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658409}