[Chromecast] Add //base:prefs as dependency of //chromecast/base
[Chromecast] Add //base:prefs as dependency of //chromecast/base

BUG=None
TEST=gncheck (through internal script)
R=slan@chromium.org, halliwell@chromium.org

Review URL: https://codereview.chromium.org/1559143003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#367668}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk