fix VerifyKeyEvent duplicate symbol errors

Some builds were failing with duplicate symbol errors about
VerifyKeyEvent. This symbol is defined by two files and each
definition is only used inside the file that contains it. This change
moves both definitions into an anonymous namespace so that they are no
longer externally visible, avoiding the build errors.

BUG=920451

Change-Id: Ic4be2f17930d0d19c10d807f65a7d7bfd6bc3edf
Reviewed-on: https://chromium-review.googlesource.com/c/1406176
Reviewed-by: Joe Downing <joedow@chromium.org>
Reviewed-by: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Bob Haarman <inglorion@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623421}
2 files changed