Call WebFrameWidget::setVisibilityState on RFI::WasShown

Call WebFrameWidget::setVisibilityState on RFI::WasShown

The call to WebViewImpl::setVisibilityState updates Blink's Page state
correctly, but was not notifying the WebFrameWidget's LayerTreeHost.

This patch calls a newly added method in WebFrameWidget that resolves
some rendering issues.

BUG=450674
Committed: https://crrev.com/cafd1ace2d7b52f1fcb4efd04d64af51768ec5c9
Cr-Commit-Position: refs/heads/master@{#318709}

[kenrb, 2015-02-27 16:09:33]

kenrb@chromium.org changed reviewers:
+ nasko@chromium.org

[kenrb, 2015-02-27 16:10:06]

Nasko: PTAL?

I think this is trivial, and is the Chromium side for
https://codereview.chromium.org/955143002/, which I hope to be landing shortly.

[nasko, 2015-02-27 16:39:18]

LGTM

[kenrb, 2015-03-02 15:13:26]

The CQ bit was checked by kenrb@chromium.org

[commit-bot: I haz the power, 2015-03-02 15:14:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/958973002/1

[commit-bot: I haz the power, 2015-03-02 16:27:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-02 16:28:30]

Patchset 1 (id:??) landed as
https://crrev.com/cafd1ace2d7b52f1fcb4efd04d64af51768ec5c9
Cr-Commit-Position: refs/heads/master@{#318709}