GitLab

This
- reduces unnecessary calls from native to java.
- makes it possible to add observer in native side.

Bug: 1042048
Change-Id: I0e5c32b98adfb56ac408556f9a0fcbd209b5813c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2001747Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732264}