cros: Touchable menus and notification indicators under different flags

Put touchable app context menus and notification indicators under two
different flags.

The notification indicator flag will also control the notifications in
context menu feature.

These features are still very related, but the ability to enable
them selectively is desirable for dogfooding.

Bug: 845316
Change-Id: Id30715dae05fe50c7d4eed9a462df13ccd1cec6c
Reviewed-on: https://chromium-review.googlesource.com/1068149
Reviewed-by: Xiyuan Xia <[email protected]>
Reviewed-by: Sadrul Chowdhury <[email protected]>
Commit-Queue: Alex Newcomer <[email protected]>
Cr-Commit-Position: refs/heads/master@{#562048}
15 files changed