debugd: Provide RunModemCommand API to run modem AT commands.

The API is required because communication with the serial interface
requires root privileges. The API will be used to implement the
corresponding crosh modem commands through DBus.

BUG=chrome-os-partner:17809
TEST=unit tests; tested on device along with relevant 'modem' script CL by
issuing relevant modem commands

Reviewed-on: https://gerrit.chromium.org/gerrit/44399
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Elly Jones <ellyjones@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Commit-Queue: Darin Petkov <petkov@chromium.org>
(cherry picked from commit c0d2872d8cf0330bdcb560830ce89362211d16dd)

Change-Id: I59495ed694f103bac0af3d9c286817754e1b16d3
Reviewed-on: https://gerrit.chromium.org/gerrit/45061
Commit-Queue: Darin Petkov <petkov@chromium.org>
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
8 files changed
tree: b142f86447be3045db26383ef9a4b26bed468a78
  1. doc/
  2. share/
  3. src/
  4. .gitignore
  5. Makefile
  6. OWNERS
  7. README