As a minimum, I think we need to:
- Set blink::WebScreenInfo::deviceScaleFactor in oxide::qt::RenderWidgetHostView::GetScreenInfo(). QScreen::devicePixelRatio() seems to be what we want here
- Implementations of content::RenderWIdgetHostView::GetViewBounds() should return bounds in device-independent pixels. We currently return device pixels directly from QQuickItem.. I would also add a new virtual function oxide::RenderWidgetHostView::GetPixelBounds()
- Audit oxide::qt::RenderWidgetHostView::AllocBackingStore() - The size is device independent, we need to convert this to device pixels to initialize the pixmap in oxide::qt::BackingStore::BackingStore()
- Audit oxide::qt::BackingStore::PaintToBackingStore() - I think bitmap_rect and copy_rects are in device independent pixels.
- Audit oxide::RenderWidgetHostView::DidUpdateBackingStore() - scroll_rect and copy_rects are device independent.
