Implement tray item for note taking lock screen app
The item is displayed in system tray status area when lock screen note
action is available - the lock screen note creation tray item is
updated by observing TrayAction state for lock screen notes.
The item is visible only in two states:
kAvailable - the item is actionable
kLaunching - the item is not actionable
The item is only visible on lock screen (given that it represents an
action handler for new note action on lock screen), regardless of the
TrayAction state - even though Chrome should eventually ensure that the
state is properly updated when user session is unlocked.
When the tray item is clicked, a request will be sent to Chrome to handle
new lock screen note using mojom::TrayActionClient interface.
BUG=716081
Review-Url: https://codereview.chromium.org/2864843002
Cr-Commit-Position: refs/heads/master@{#470621}
6 files changed
