The new property is accessibilityFeatures.animationPolicy.
The new field for animation policy is added to Web Preference and the new profile is added.
accessibility_features.json is not specific to chromeos any more.
When the animation policy is updated through the extension,
Web preference is updated and WebSettings from Blink is updated.

BUG=3690

Review URL: https://codereview.chromium.org/785723002

Cr-Commit-Position: refs/heads/master@{#315330}