Kindle Fire UA strings in remote debugger are out of date

This updates the User Agents to reflect the user agents used by the
Silk web browser on Amazon Kindle Fire devices.

This includes all current Kindle devices for the "Devices" tab,
as well as generic Silk UAs for the User Agent tab.

BUG=353396
NOTRY=true

Review URL: https://codereview.chromium.org/196383028

git-svn-id: svn://svn.chromium.org/blink/trunk@171268 bbb929c8-8fbe-4397-9dbb-9b2b20218538