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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

Review URL: https://codereview.chromium.org/958973002

Cr-Commit-Position: refs/heads/master@{#318709}