Disable 'Ok Google' hotwording on desktop Chrome.

This feature has been removed completely from Windows, Mac and Linux
builds of Chrome. ChromeOS is unaffected.

This removes the checkbox from chrome://settings and the prompt to
activate it from the google.com search page.

BUG=506098,507384
TEST=On ChromeOS (official builds), go to chrome://settings. Should see "Enable Ok Google" checkbox.
TEST=On Windows Chrome (official builds), go to chrome://settings. Should NOT see "Enable Ok Google" checkbox.

Review URL: https://codereview.chromium.org/1264973002

Cr-Commit-Position: refs/heads/master@{#342245}
2 files changed