GitLab

Has shelf layout manager notify the status area widget that the locale
has changed, which then forwards the notification to tray items, and
unified tray items so they can update any cached strings (e.g. string
used for item tooltips).

This added pure virtual  HandleLocaleChange() method to TrayItemView and
TrayBackgroundView to make sure that tray items added in future
implement this.

BUG=1077147, 1076318, 1076310, 1076302, 1076301

Change-Id: I09ae5b891a383a89eb748cd27f86aab8c461f3d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2222949Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Reviewed-by: Tim Song <tengs@chromium.org>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774936}