Moved |openedByDOM| to WebState's CreateParams and public interface.

WebContents::CreateParams also includes opened by DOM information.  Our
interface diverges slightly because web// requires that information to
be exposed, while content// handles that logic internally via render
view hosts.

BUG=454984, 620045, 620045

Review-Url: https://codereview.chromium.org/2755823002
Cr-Commit-Position: refs/heads/master@{#458274}
33 files changed