Better feedback for empty completion lists

[stevemessick]

When no code completion proposals can be found after Ctl-Space is typed the user should be shown a message in the style of the completion list saying nothing is available. Currently, red text appears in the lower-left corner of the screen but that is easy ignore. An empty completion list after typing '.' should not cause a message to appear.

[stevemessick]

Added Area-Editor label.

[danrubel]

[user feedback]

• control-space auto suggestion is a bit slow and indecisive at times and shows nothing.

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  Changed the title to: "Better feedback for empty completion lists (+1)".

[stevemessick]

Added this to the M1 milestone.

[stevemessick]

Removed this from the M1 milestone.
Added this to the Later milestone.
Changed the title to: "Better feedback for empty completion lists".

[DartBot]

This comment was originally written by amouravski@google.com

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Added Editor-Usability label.

[clayberg]

cc @stevemessick.
Set owner to @scheglov.

[kasperl]

Removed this from the Later milestone.
Added Oldschool-Milestone-Later label.

[sethladd]

Added AssumedStale label.

[clayberg]

Added this to the 1.6 milestone.