Telemetry: Catch LookupError exception and mark as failure.
Telemetry: Catch LookupError exception and mark as failure.

Because the smoothness measurement may throw LookupError exceptions,
PageRunner::_RunPage() catches those and reports a failure. Before,
this exception wasn't caught and thus caused Telemetry to crash.

BUG=238864

Review URL: https://chromiumcodereview.appspot.com/23726017

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@220977 0039d316-1c4b-4281-b951-d872f2087c98

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