What steps will reproduce the problem?
1. Render the attached file (warning.svg) to PDF
2. Open up the PDF in your favorite viewer.
3. Zoom in. Background is pixelated.
What is the expected output? What do you see instead?
A non-pixelated background (smooth "gradient") is expected, but instead it shows a pixelated background.
Branch from this bug: https://code.google.com/p/chromium/issues/detail?id=99458
The likely cause is that the effect is a Gaussian blur, which isn't natively supported in PDF, so we have to output a raster version. A fix would probably to allow a higher (perhaps even variable?) resolution for raster effects when exporting to PDF.