CrOS: Eliminate unused strings from chromeos_strings.grdp

Includes a minor change to check_grd_for_unused_strings.py

Found running the following with the change to
check_grd_for_unused_strings.py:
 ./tools/check_grd_for_unused_strings.py chrome \
    chrome/app/chromeos_strings.grdp

Some of these came from the switch to the new Settings UI and were
missed, some have just been lingering for a very long time.

Bug: 771795, 783396
Change-Id: If6d9ab01f909c69d6375459d314e97ce3633ceaf
Reviewed-on: https://chromium-review.googlesource.com/762383
Reviewed-by: Michael Giuffrida <[email protected]>
Reviewed-by: Devlin <[email protected]>
Reviewed-by: Scott Graham <[email protected]>
Commit-Queue: Steven Bennetts <[email protected]>
Cr-Commit-Position: refs/heads/master@{#515629}
diff --git a/tools/check_grd_for_unused_strings.py b/tools/check_grd_for_unused_strings.py
index 21afc8a..7e5e919 100755
--- a/tools/check_grd_for_unused_strings.py
+++ b/tools/check_grd_for_unused_strings.py
@@ -119,7 +119,7 @@
   src_dirs = []
   grd_files = []
   for arg in sys.argv[1:]:
-    if arg.lower().endswith('.grd'):
+    if arg.lower().endswith('.grd') or arg.lower().endswith('.grdp'):
       grd_files.append(arg)
     else:
       src_dirs.append(arg)