Remove early return for empty invalid regions from
ClientTiledPaintedLayer::RenderHighPrecision so that
ClientMultiTiledLayerBuffer::PaintThebes is called even when the region
to paint is empty. This ensures that the tile buffer will free unused
tiles in cases where no new painting is required but the valid region
has shrunk.
Add replacement early returns into ClientMultiTiledLayerBuffer to avoid
as much needless work as possible while still recalculating which tiles
are valid.
MozReview-Commit-ID: C86Pi7lRjjs
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extra : transplant_source : %F0%96H%DAn4%FE%A6%3EPf%B7%AF3%95%D6%F9o%D9/
b53bc9fd1c