GitLab

The some changes of element will not cause remove/add LayoutText,
instead, LayoutText is changed.

This patch supports the content change in this case, DidUpdateContent()
is added and invoked after new content is sent.

Bug: 952973
Change-Id: Ia530e7e71570801f1f494bd584526cc7dc3ccba8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1598310
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659145}