Unsandboxed popups may also be navigated.

If a sandboxed frame has the 'allow-popups-to-escape-sandbox' flag, it
ought to be allowed to navigate the context it opens. This patch fixes
our implementation accordingly.

BUG=577330
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/1583953005

Cr-Commit-Position: refs/heads/master@{#369702}
2 files changed