Similar to #37960, previously, `AvailHeight`, `AvailWidth`, `Height`,
`Width` ask compositor for screen metrics. This PR moves the request to
embedder.
This simplifies code, and reduces workload of compositor, which is
busier most of time.
Testing: No behaviour change. Updated some tests. `Width/Height` matches
other browsers.
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Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>