Auto merge of #1177 - kvark:hack-clip-rect, r=mrobinson
Auto merge of #1177 - kvark:hack-clip-rect, r=mrobinson

Combined clip rect workaround

There is a problem with `combined_local_viewport_rect` that makes it too tight for transformed layers. This PR attempts to work around this, not a proper fix. Having it would make the new reftest of #1169 to pass.

r? @mrobinson

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