Respect display rotation on Chrome OS.
Respect display rotation on Chrome OS.

We need to use layer->GetTargetTransform()
instead of layer->transform() as the display may be animating while we are setting the root window transform.

BUG=515561

Review URL: https://codereview.chromium.org/1712343004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#377725}

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