GitLab

+ Record dialog dismissal on Android side as kDialogClosed
+ Add metrics recording support for modal dialogs, and remove onCancel
  callback

Bug: 873236
Change-Id: Idbe990f2c70883f851bf5214dbf0a3e7b96f4260
Reviewed-on: https://chromium-review.googlesource.com/1222990Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Becky Zhou <huayinz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593634}