GitLab

SharingMessageSender replaces ResponseCallbackHelper. This ensures
SharingFCMSender does not need to surface any other API.

Bug: 1018274
Change-Id: Ieb9f7010ddeedc694fcfe72ff49c5659d758690d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895660
Commit-Queue: Himanshu Jaju <himanshujaju@chromium.org>
Reviewed-by: Alex Chau <alexchau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712218}