[Merge-M54] arc: Fix Arc app item context menu.

[Merge-M54] arc: Fix Arc app item context menu.

This fixes arc context menu. Original bug requests to make
"Show app info" menu item disable when Arc is not ready only.
This also includes following related fixes:
  1. "Show app info" is disabled until Arc is started.
  2. Before "Uninstall" was not shown when Arc is not started.
     This also makes it disable in this case for consistency.
  3. Add separator before "Uninstall/Show app info" group regardless
     "Uninstall" item is shown or not. Before, "Show app info" menu
     was not separated in case uninstall was not present.
  4. "Uninstall" shortcut is available always, regardless of
     Arc enabled or disabled.
  5. No menu items for non-existing Arc app.
TEST=Manually on the device.
TEST=Extended unit_tests.
BUG=652741
BUG=b/30646620

TBR=reviewer@chromium.org
NOTRY=true
NOPRESUBMIT=true

Review-Url: https://codereview.chromium.org/2393453002
Cr-Commit-Position: refs/heads/master@{#422831}

[khmel, 2016-10-06 01:22:27]

The CQ bit was checked by khmel@chromium.org

[commit-bot: I haz the power, 2016-10-06 01:23:10]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-06 01:25:49]

Committed patchset #1 (id:1)