permissions: Replace file:/// in permission dialogs with "This file"

Currently, the permission prompt says "file:/// wants to show
notifications" for file URLs, which isn't meaningful.

This change replaces "file:///" with "This file".

It:
1) Adds a new string for "This file"
2) Adds logic to PermissionPromptBubbleView to return the string for
   file scheme origins
4) Adds unit tests for PermissionPromptBubbleView to test this
   replacement in the accessible title

Bug: 1078920
Change-Id: I57f3a7b61786e02ae1f2132dd1c81e4b4de652d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2223933
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775822}

diff --git a/AUTHORS b/AUTHORS
index cc668c7..d0d2926 100644
--- a/AUTHORS
+++ b/AUTHORS

@@ -275,6 +275,7 @@
 Eduardo Lima (Etrunko) <eduardo.lima@intel.com>
 Edward Baker <edward.baker@intel.com>
 Edward Crossman <tedoc2000@gmail.com>
+Edward Trist <edwardtrist@gmail.com>
 Eero Häkkinen <e.hakkinen@samsung.com>
 Eero Häkkinen <eero.hakkinen@intel.com>
 Egor Starkov <egor.starkov@samsung.com>