Add policy management for on-screen keyboard.

BUG=341882

Review URL: https://codereview.chromium.org/155573003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251349 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251349
Add GYP flag to optionally enable the Hangout Services extension in
any build (not just Chrome-branded builds).

BUG=343567

Review URL: https://codereview.chromium.org/163583004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251350 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251350