Restore TWA snackbar when Chrome comes back to foreground

SnackbarManager removes all snackbars when Chrome goes to background,
so we must restore TWA snackbar when coming back to foreground

Bug: 923861
Change-Id: I9480fb6e4aace42890abad19433ff612fabece19
Reviewed-on: https://chromium-review.googlesource.com/c/1426706
Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Commit-Queue: Pavel Shmakov <pshmakov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625155}
1 file changed