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Currently, both the plugin and the UI track the state of two-up-view.
Additionally, the state tracked by the plugin is consistently sent to
the UI.

While two-up-view can only be invoked on through the UI, the feature
actually occurs asynchronously. It would be better to update the UI
state with that of the plugin.

Change-Id: Id0b40c2fa0d7d4eb029bbb06d8eb162871938385
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631360
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844870}