Remove stale Field Trial code
Remove stale Field Trial code

Dummy FindValue() call isn't needed to sync the Field Trial
configuration between browser and renderers any more.

BUG=n/a

Review URL: https://codereview.chromium.org/1580233005

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#373469}

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