Remove disabled annotation on startup.warm.chrome_signin reference.
Remove disabled annotation on startup.warm.chrome_signin reference.

R=dtu,bokan
BUG=499312

Review URL: https://codereview.chromium.org/1642783002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#376803}

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