Add verification that google URL has a valid TLD.

There are a number of privacy-sensitive checks that we make using this
function. In order to ensure that the URLs really belong to Google, add
a check that TLD has been registered by Google.

BUG=665624

Review-Url: https://codereview.chromium.org/2498113003
Cr-Commit-Position: refs/heads/master@{#441421}
4 files changed