GitLab

* Move code that was in CellularSetupDialogUI to CellularSetupImpl so
  that both OsSettingsUI and CellularSetupDialogUI can use it.
* Bind OsSettingsUI to mojo interface.
* Add cellular setup localized strings to internet section so they
  will be displayed in the shared UI.

Bug: 1093185
Change-Id: I044e8af8f1cee07a1dda1d7ee0ada38e2c3fe6d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2349389Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Azeem Arshad <azeemarshad@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800427}