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Previously we were writing to loadTimeData in
ChromeMediaAppUIDelegate::PopulateLoadTimeData but it was not made
available via window.loadTimeData.

This change adds load_time_data.js to our untrusted context so we can
make use of it.

Note: "/strings.js" is required to ensure LoadTimeData is non empty.

Now loadTimeData looks like
```
{
   "data_":{
      "appLocale":"en-GB",
      "fontfamily":"Roboto, sans-serif",
      "fontsize":"75%",
      "language":"en",
      "textdirection":"ltr"
   }
}
```

Side note: also fixes html lint (don't close single tags) & sorts DEPS

Bug: b/170160681, b/170423915
Change-Id: I4d73037577534ef516641e2acf86c45126d444f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2437582
Commit-Queue: David Lei <dlei@google.com>
Auto-Submit: David Lei <dlei@google.com>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815503}