am 2458f2a1: cherrypick Change-Id: I60c74919ab3df359f47e5052bcc1469318a5b821 add notice about large screen devices and the "mobile" string in user agent

* commit '2458f2a1ccf13a9f33c21d8aff260baefac9edb8':
  cherrypick Change-Id: I60c74919ab3df359f47e5052bcc1469318a5b821 add notice about large screen devices and the "mobile" string in user agent