Fix translation extraction failure.
The newly added string IDS_DOWNLOAD_FAILED_MESSAGE has the same contents
as the existing string IDS_DOWNLOAD_STATUS_DOWNLOADED_TITLE, except for
different text inside the placeholder. This breaks some assumptions in
the translation pipeline. To fix it, add a "meaning" attribute to
IDS_DOWNLOAD_FAILED_MESSAGE, which causes the strings to have different
IDs and fixes the problem.
TBR=qinmin@chromium.org
Review URL: https://codereview.chromium.org/
1354793005
Cr-Commit-Position: refs/heads/master@{#350076}