Telemetry fix: .wpr metadata layer with missing metadata again.
Telemetry fix: .wpr metadata layer with missing metadata again.

(Fixing https://codereview.chromium.org/11881051/ .)

TBR=tonyg
BUG=155660
NOTRY=true


Review URL: https://chromiumcodereview.appspot.com/12208128

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@181909 0039d316-1c4b-4281-b951-d872f2087c98

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