Add targetsAtLeastO() helper function

This adds the targetsAtLeastO() helper function to BuildInfo. I also
updated the check we were using for HTTPS clear text to use this
instead of manually checking targetSdkVersion.

This helper should be updated once the SDK level for O has been
finalized.

BUG=688556

Review-Url: https://codereview.chromium.org/2745663002
Cr-Commit-Position: refs/heads/master@{#456128}
2 files changed